[libc] support out of tree build with dynlibs (#97959)

Author: SchrodingerZhu

libc/utils/HdrGen/CMakeLists.txt

@@ -1,6 +1,8 @@
 include(TableGen)
 
-set(LLVM_LINK_COMPONENTS Support)
+if (NOT LLVM_LINK_LLVM_DYLIB)
+  set(LLVM_LINK_COMPONENTS Support)
+endif()
 
 add_tablegen(libc-hdrgen LIBC
   Command.h

libc/utils/LibcTableGenUtil/CMakeLists.txt

@@ -1,9 +1,13 @@
+if (NOT LLVM_LINK_LLVM_DYLIB)
+  set(flags "DISABLE_LLVM_LINK_LLVM_DYLIB;LINK_COMPONENTS;Support;TableGen")
+else()
+  set(flags "LINK_COMPONENTS;TableGen")
+endif()
 add_llvm_library(
   LibcTableGenUtil
   APIIndexer.cpp
   APIIndexer.h
-  DISABLE_LLVM_LINK_LLVM_DYLIB
-  LINK_COMPONENTS Support TableGen
+  ${flags}
 )
 target_include_directories(LibcTableGenUtil PUBLIC ${LIBC_SOURCE_DIR})
 target_include_directories(LibcTableGenUtil PRIVATE ${LLVM_INCLUDE_DIR} ${LLVM_MAIN_INCLUDE_DIR})