docs: Update to reference host_platform instead of target_platform

Update the documentation throughout to replace the references to
`target_platform` with `host_platform` where appropriate.  That said,
unless I've missed some fine point, this means pretty much everywhere.

Author: mgorny

docs/compilers.md

@@ -3,7 +3,7 @@
 To use a compiler in your project, it's best to use the `${{ compiler('lang')
 }}` template function. The compiler function works by taking a language,
 determining the configured compiler for that language, and adding some
-information about the target platform to the selected compiler. To configure a
+information about the host platform to the selected compiler. To configure a
 compiler for a specific language, the `variant_config.yaml` file can be used.
 
 For example, in a recipe that uses a C-compiler, you can use the following code:
@@ -35,7 +35,7 @@ variant config.
 
 Cross-compilation is supported by `rattler-build` and the compiler template
 function is part of what makes it possible. When you want to cross-compile from
-`linux-64` to `linux-aarch64` (i.e. intel to ARM), you can pass `--target-platform
+`linux-64` to `linux-aarch64` (i.e. intel to ARM), you can pass `--host-platform
 linux-aarch64` to the `rattler-build` command. This will cause the compiler
 template function to select a compiler that is configured for `linux-aarch64`.
 The above example would resolve to `gcc_linux-aarch64 9.3.0`. Provided that the
@@ -57,7 +57,7 @@ build:
   - cmake
   - ${{ compiler('c') }}
 # packages that we want to link against in the architecture we are
-# cross-compiling to the target_platform
+# cross-compiling to the host_platform
 host:
   - libcurl
   - openssl

docs/index.md

@@ -324,7 +324,7 @@ For the `curl` library recipe, two additional script files (`build.sh` and `buil
 # Get an updated config.sub and config.guess
 cp $BUILD_PREFIX/share/libtool/build-aux/config.* .
 
-if [[ $target_platform =~ linux.* ]]; then
+if [[ $host_platform =~ linux.* ]]; then
     USESSL="--with-openssl=${PREFIX}"
 else
     USESSL="--with-secure-transport"

docs/reference/jinja.md

@@ -8,11 +8,11 @@ functions and filters that can be used in the recipe.
 ### The compiler function
 
 The compiler function can be used to put together a compiler that works for the
-current platform and the compilation "`target_platform`". The syntax looks like:
+current platform and the compilation "`host_platform`". The syntax looks like:
 `${{ compiler('c') }}` where `'c'` signifies the programming language that is
 used.
 
-This function evaluates to `<compiler>_<target_platform> <compiler_version>`.
+This function evaluates to `<compiler>_<host_platform> <compiler_version>`.
 For example, when compiling _on_ `linux` and _to_ `linux-64`, this function
 evaluates to `gcc_linux-64`.
 
@@ -38,9 +38,9 @@ c_compiler_version:
 ```
 
 The variables shown above would select the `clang` compiler in version `9.0`.
-Note that the final output will still contain the `target_platform`, so that the
+Note that the final output will still contain the `host_platform`, so that the
 full compiler will read `clang_linux-64 9.0` when compiling with
-`--target-platform linux-64`.
+`--host-platform linux-64`.
 
 `rattler-build` defines some default compilers for the following languages
 (inherited from `conda-build`):
@@ -54,11 +54,11 @@ full compiler will read `clang_linux-64 9.0` when compiling with
 
 The `stdlib` function closely mirrors the compiler function. It can be used to
 put together a standard library that works for the current platform and the
-compilation "`target_platform`".
+compilation "`host_platform`".
 
 Usage: `${{ stdlib('c') }}`
 
-Results in `<stdlib>_<target_platform> <stdlib_version>`. And uses the variant
+Results in `<stdlib>_<host_platform> <stdlib_version>`. And uses the variant
 variables `<lang>_stdlib` and `<lang>_stdlib_version` to influence the output.
 
 #### Usage in a recipe:

docs/selectors.md

@@ -54,7 +54,7 @@ host:
 Other examples often found in the wild:
 
 ```yaml
-if: build_platform != target_platform ... # true if cross-platform build
+if: build_platform != host_platform ... # true if cross-platform build
 if: osx and arm64 ... # true for apple silicon (osx-arm64)
 if: linux and (aarch64 or ppc64le)) ... # true for linux ppc64le or linux-aarch64
 ```
@@ -65,12 +65,13 @@ The following variables are available during rendering of the recipe:
 
 | Variable             | Description                                                            |
 |----------------------|------------------------------------------------------------------------|
-| `target_platform`    | the configured `target_platform` for the build                         |
 | `build_platform`     | the configured `build_platform` for the build                          |
-| `linux`              | "true" if `target_platform` is Linux                                   |
-| `osx`                | "true" if `target_platform` is OSX / macOS                             |
-| `win`                | "true" if `target_platform` is Windows                                 |
-| `unix`               | "true" if `target_platform` is a Unix (macOS or Linux)                 |
+| `host_platform`      | the configured `host_platform` for the build                           |
+| `target_platform`    | the configured `target_platform` for the build                         |
+| `linux`              | "true" if `host_platform` is Linux                                     |
+| `osx`                | "true" if `host_platform` is OSX / macOS                               |
+| `win`                | "true" if `host_platform` is Windows                                   |
+| `unix`               | "true" if `host_platform` is a Unix (macOS or Linux)                   |
 | `x86`, `x86_64`      | x86 32/64-bit Architecture                                             |
 | `aarch64`, `arm64`   | 64-bit Arm (these are the same but are both supported for legacy)      |
 | `armV6l`, `armV7l`   | 32-bit Arm                                                             |
@@ -149,9 +150,9 @@ Some notable options are:
 ```yaml
 - if: python == "3.8" # equal
 - if: python != "3.8" # not equal
-- if: python and linux # true if python variant is set and the target_platform is linux
-- if: python and not linux # true if python variant is set and the target_platform is not linux
-- if: python and (linux or osx) # true if python variant is set and the target_platform is linux or osx
+- if: python and linux # true if python variant is set and the host_platform is linux
+- if: python and not linux # true if python variant is set and the host_platform is not linux
+- if: python and (linux or osx) # true if python variant is set and the host_platform is linux or osx
 ```
 
 [minijinja]: https://github.com/mitsuhiko/minijinja

docs/tutorials/rust.md

@@ -41,7 +41,7 @@ about:
 
 !!! note
     The `${{ compiler(...) }}` functions are very useful in the context of cross-compilation.
-    When the function is evaluated it will insert the correct compiler (as selected with the variant config) as well the `target_platform`.
+    When the function is evaluated it will insert the correct compiler (as selected with the variant config) as well the `host_platform`.
     The "rendered" compiler will look like `rust_linux-64` when you are targeting the `linux-64` platform.
 
     You can read more about this in the [cross-compilation](../compilers.md) section.