Fixes OTELCPP_BUILD_DLL and markdownlint

Author: owent

INSTALL.md

@@ -376,8 +376,8 @@ and user may have to customize it further before using it as distribution.
 - Windows : NuGet, zip
 
 This requires platform specific package generators already installed. The package
-generation can subsequently be enabled by using OTELCPP_BUILD_PACKAGE option during cmake
-configuration
+generation can subsequently be enabled by using OTELCPP_BUILD_PACKAGE option
+during cmake configuration
 
    ```console
    $ cd opentelemetry-cpp

docs/abi-version-policy.md

@@ -298,8 +298,8 @@ the given ABI is no longer available.
 
 The build files are the source of truth for which ABI version is currently
 experimental versus stable. In CMake, the experimental version is the
-`OTELCPP_WITH_ABI_VERSION_*` option labeled `EXPERIMENTAL` in `CMakeLists.txt`, and it
-is off by default; any version without that label is stable.
+`OTELCPP_WITH_ABI_VERSION_*` option labeled `EXPERIMENTAL` in `CMakeLists.txt`,
+and it is off by default; any version without that label is stable.
 
 The following sections describe the migration path from one ABI (v1) to the
 next (v2).

ext/src/CMakeLists.txt

@@ -23,6 +23,6 @@ if(OTELCPP_WITH_HTTP_CLIENT_CURL
   otel_add_component(COMPONENT ext_http TARGETS opentelemetry_http_client)
 endif()
 
-if(DEFINED OTELCPP_BUILD_DLL)
+if(OTELCPP_BUILD_DLL)
   add_subdirectory(dll)
 endif()