[compiler-rt][cmake] Add option to control shared library builds

This patch makes the compiler-rt to respect `BUILD_SHARED_LIBS` to
control whether shared libraries should be built for runtime libraries
in compiler-rt. By default, this option is set to ON, allowing shared
libraries to be built. If set to OFF, shared libraries will not be
built, which can be useful for projects that do not require them
or when building for environments where shared libraries are still
not yet matured, such as WebAssembly/WASI.

Author: kateinoigakukun

compiler-rt/CMakeLists.txt

@@ -91,6 +91,9 @@ 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)
 
+option(BUILD_SHARED_LIBS "Build all libraries as shared libraries in addition to static libraries" ON)
+mark_as_advanced(BUILD_SHARED_LIBS)
+
 if(FUCHSIA)
   set(COMPILER_RT_HWASAN_WITH_INTERCEPTORS_DEFAULT OFF)
 else()

compiler-rt/cmake/Modules/AddCompilerRT.cmake

@@ -169,6 +169,10 @@ function(add_compiler_rt_runtime name type)
             "type argument must be OBJECT, STATIC, SHARED or MODULE")
     return()
   endif()
+  if(type STREQUAL "SHARED" AND NOT BUILD_SHARED_LIBS)
+    message(STATUS "Skipping shared library ${name} because BUILD_SHARED_LIBS is OFF")
+    return()
+  endif()
   cmake_parse_arguments(LIB
     ""
     "PARENT_TARGET"