[compiler-rt] [llvm] [cmake] Refactor DIA SDK detection into FindDIASDK module (PR #160354)

[Saleem Abdulrasool via llvm-commits]

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@@ -0,0 +1,74 @@
+# Finds the Microsoft DIA SDK and sets DIASDK_FOUND and related variables.
+#
+# This module is intended to be used both internally by LLVM's build system and
+# by consuming projects when loading LLVMConfig.cmake.
+#
+# LLVM_WINSYSROOT may be set for locating the DIA SDK.
+#
+# If successful, the following variables will be defined:
+#   DIASDK_FOUND
+#   DIASDK_INCLUDE_DIR
+#   DIASDK_LIBRARIES
+#
+# Additionally, the following import target will be defined:
+#   DIASDK::Diaguids
+
+if(NOT WIN32)
+  set(DIASDK_FOUND FALSE)
+  return()
+endif()
+
+if(LLVM_WINSYSROOT)
+  set(MSVC_DIA_SDK_DIR "${LLVM_WINSYSROOT}/DIA SDK" CACHE PATH
+      "Path to the DIA SDK")
+else()
+  set(MSVC_DIA_SDK_DIR "$ENV{VSINSTALLDIR}DIA SDK" CACHE PATH
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compnerd wrote:

I guess this is the original code, but if `VSINSTALLDIR` is not set in the environment, this will default to `DIA SDK`.

https://github.com/llvm/llvm-project/pull/160354