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

[Petr Hosek 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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petrhosek wrote:

Using `BUILD_SHARED_LIBS` is the correct way. `LLVM_ENABLE_PROJECTS=compiler-rt` is not the right way to build compiler-rt for the host platform and we'll be [removing support for building compiler-rt that way after LLVM 21 branches](https://github.com/llvm/llvm-project/blob/83fbd86909111510f973d8e1c4214022368ef810/llvm/CMakeLists.txt#L188-L193).

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