[compiler-rt] [compiler-rt][cmake] Add option to control shared library builds (PR #139042)

[Yuta Saito via llvm-commits]

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@@ -91,6 +91,13 @@ mark_as_advanced(COMPILER_RT_SCUDO_STANDALONE_BUILD_SHARED)
 option(COMPILER_RT_BUILD_SCUDO_STANDALONE_WITH_LLVM_LIBC "Build SCUDO standalone with LLVM's libc headers" OFF)
 mark_as_advanced(COMPILER_RT_BUILD_SCUDO_STANDALONE_WITH_LLVM_LIBC)
 
+set(COMPILER_RT_BUILD_SHARED_LIBS_DEFAULT ON)
+if(CMAKE_SYSTEM_NAME STREQUAL "WASI")
+  set(COMPILER_RT_BUILD_SHARED_LIBS_DEFAULT OFF)
+endif()
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kateinoigakukun wrote:

The `CMAKE_SYSTEM_NAME` variable here points to the target platform where the runtime library runs on, not the platform where compiler runs. The LLVM CMake infrastructure uses `ExternalProject_Add` in the unified build of compiler + runtime libs, and it passes through most of CMake args **except for `CMAKE_SYSTEM_NAME`** and a few other exceptions. So CMake scripts in compiler-rt can assume `CMAKE_SYSTEM_NAME` is the target platform, not host.

https://github.com/llvm/llvm-project/pull/139042