[libc] Only add -ffreestanding flag in full build mode.

Only add -ffreestanding flag in full build mode.

Reviewed By: sivachandra

Differential Revision: https://reviews.llvm.org/D158652

Author: lntue

libc/cmake/modules/LLVMLibCObjectRules.cmake

@@ -21,7 +21,12 @@ function(_get_common_compile_options output_var flags)
   set(compile_options ${LIBC_COMPILE_OPTIONS_DEFAULT} ${ARGN})
   if(LLVM_COMPILER_IS_GCC_COMPATIBLE)
     list(APPEND compile_options "-fpie")
-    list(APPEND compile_options "-ffreestanding")
+
+    if(LLVM_LIBC_FULL_BUILD)
+      # Only add -ffreestanding flag in full build mode.
+      list(APPEND compile_options "-ffreestanding")
+    endif()
+
     list(APPEND compile_options "-fno-builtin")
     list(APPEND compile_options "-fno-exceptions")
     list(APPEND compile_options "-fno-lax-vector-conversions")

libc/cmake/modules/LLVMLibCTestRules.cmake

@@ -156,8 +156,14 @@ function(create_libc_unittest fq_target_name)
   )
   target_compile_options(
     ${fq_build_target_name}
-    PRIVATE -fpie -ffreestanding ${LIBC_COMPILE_OPTIONS_DEFAULT}
+    PRIVATE -fpie ${LIBC_COMPILE_OPTIONS_DEFAULT}
   )
+  if(LLVM_LIBC_FULL_BUILD)
+    target_compile_options(
+      ${fq_build_target_name}
+      PRIVATE -ffreestanding
+    )
+  endif()
   if(LIBC_UNITTEST_COMPILE_OPTIONS)
     target_compile_options(
       ${fq_build_target_name}