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

[lntue]

Summary

Only add -ffreestanding flag in full build mode.

[sivachandra]

Can you adjust here also: https://github.com/llvm/llvm-project/blob/main/libc/cmake/modules/LLVMLibCTestRules.cmake#L159

[lntue]

Only add -ffreestanding to unit tests in full build mode.

[lntue]

In D158652#4611128, @sivachandra wrote:

Can you adjust here also: https://github.com/llvm/llvm-project/blob/main/libc/cmake/modules/LLVMLibCTestRules.cmake#L159

Done.

[sivachandra]

libc/cmake/modules/LLVMLibCTestRules.cmake

170

A cleaner approach is likely:

target_compile_options(
  ${fq_build_target_name}
  PRIVATE -fpie ${LIBC_COMPILE_OPTIONS_DEFAULT})
)
if(LLVM_LIBC_FULL_BUILD)
  target_compile_options(${fq_build_target_name} PRIVATE -ffreestanding)
endif()

[lntue]

Address comment.

libc/cmake/modules/LLVMLibCObjectRules.cmake

function(_get_common_compile_options output_var flags)
   endif()
   if((${round} GREATER -1) AND (LIBC_CPU_FEATURES MATCHES "SSE4_2"))
     set(ADD_SSE4_2_FLAG TRUE)
   endif()
 
   set(compile_options ${LIBC_COMPILE_OPTIONS_DEFAULT} ${ARGN})
   if(LLVM_COMPILER_IS_GCC_COMPATIBLE)
     list(APPEND compile_options "-fpie")
+
+    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")
     list(APPEND compile_options "-fno-unwind-tables")
     list(APPEND compile_options "-fno-asynchronous-unwind-tables")
     list(APPEND compile_options "-fno-rtti")
     list(APPEND compile_options "-Wall")
     list(APPEND compile_options "-Wextra")

libc/cmake/modules/LLVMLibCTestRules.cmake

function(create_libc_unittest fq_target_name)
   target_include_directories(
     ${fq_build_target_name}
     PRIVATE
       ${LIBC_SOURCE_DIR}
       ${LIBC_INCLUDE_DIR}
   )
   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}
       PRIVATE ${LIBC_UNITTEST_COMPILE_OPTIONS}
     )
   endif()
   if(NOT LIBC_UNITTEST_CXX_STANDARD)
     set(LIBC_UNITTEST_CXX_STANDARD ${CMAKE_CXX_STANDARD})
   endif()
   set_target_properties(
     ${fq_build_target_name}
     PROPERTIES