Exposed supported platform triples lists (#797)

* Exposed supported systems list and other such information.

* Don't expose these to avoid confusion

* Remove android fixes

Author: UebelAndre

rust/platform/platform.bzl

@@ -3,45 +3,12 @@
 load("@bazel_skylib//lib:selects.bzl", "selects")
 load(
     ":triple_mappings.bzl",
+    "SUPPORTED_PLATFORM_TRIPLES",
     "cpu_arch_to_constraints",
     "system_to_constraints",
     "triple_to_constraint_set",
 )
 
-# All T1 Platforms should be supported, but aren't, see inline notes.
-_SUPPORTED_T1_PLATFORM_TRIPLES = [
-    "i686-apple-darwin",
-    "i686-pc-windows-msvc",
-    "i686-unknown-linux-gnu",
-    "x86_64-apple-darwin",
-    "x86_64-pc-windows-msvc",
-    "x86_64-unknown-linux-gnu",
-    # N.B. These "alternative" envs are not supported, as bazel cannot distinguish between them
-    # and others using existing @platforms// config_values
-    #
-    #"i686-pc-windows-gnu",
-    #"x86_64-pc-windows-gnu",
-]
-
-# Some T2 Platforms are supported, provided we have mappings to @platforms// entries.
-# See @rules_rust//rust/platform:triple_mappings.bzl for the complete list.
-_SUPPORTED_T2_PLATFORM_TRIPLES = [
-    "aarch64-apple-darwin",
-    "aarch64-apple-ios",
-    "aarch64-linux-android",
-    "aarch64-unknown-linux-gnu",
-    "arm-unknown-linux-gnueabi",
-    "i686-linux-android",
-    "i686-unknown-freebsd",
-    "powerpc-unknown-linux-gnu",
-    "s390x-unknown-linux-gnu",
-    "wasm32-unknown-unknown",
-    "wasm32-wasi",
-    "x86_64-apple-ios",
-    "x86_64-linux-android",
-    "x86_64-unknown-freebsd",
-]
-
 _SUPPORTED_CPU_ARCH = [
     "aarch64",
     "arm",
@@ -88,7 +55,7 @@ def declare_config_settings():
         actual = ":darwin",
     )
 
-    all_supported_triples = _SUPPORTED_T1_PLATFORM_TRIPLES + _SUPPORTED_T2_PLATFORM_TRIPLES
+    all_supported_triples = SUPPORTED_PLATFORM_TRIPLES
     for triple in all_supported_triples:
         native.config_setting(
             name = triple,

rust/platform/triple_mappings.bzl

@@ -1,5 +1,41 @@
 """Helpers for constructing supported Rust platform triples"""
 
+# All T1 Platforms should be supported, but aren't, see inline notes.
+SUPPORTED_T1_PLATFORM_TRIPLES = [
+    "i686-apple-darwin",
+    "i686-pc-windows-msvc",
+    "i686-unknown-linux-gnu",
+    "x86_64-apple-darwin",
+    "x86_64-pc-windows-msvc",
+    "x86_64-unknown-linux-gnu",
+    # N.B. These "alternative" envs are not supported, as bazel cannot distinguish between them
+    # and others using existing @platforms// config_values
+    #
+    #"i686-pc-windows-gnu",
+    #"x86_64-pc-windows-gnu",
+]
+
+# Some T2 Platforms are supported, provided we have mappings to @platforms// entries.
+# See @rules_rust//rust/platform:triple_mappings.bzl for the complete list.
+SUPPORTED_T2_PLATFORM_TRIPLES = [
+    "aarch64-apple-darwin",
+    "aarch64-apple-ios",
+    "aarch64-linux-android",
+    "aarch64-unknown-linux-gnu",
+    "arm-unknown-linux-gnueabi",
+    "i686-linux-android",
+    "i686-unknown-freebsd",
+    "powerpc-unknown-linux-gnu",
+    "s390x-unknown-linux-gnu",
+    "wasm32-unknown-unknown",
+    "wasm32-wasi",
+    "x86_64-apple-ios",
+    "x86_64-linux-android",
+    "x86_64-unknown-freebsd",
+]
+
+SUPPORTED_PLATFORM_TRIPLES = SUPPORTED_T1_PLATFORM_TRIPLES + SUPPORTED_T2_PLATFORM_TRIPLES
+
 # CPUs that map to a "@platforms//cpu entry
 _CPU_ARCH_TO_BUILTIN_PLAT_SUFFIX = {
     "aarch64": "aarch64",