[libc] Output all headers with LIBC_CONF_OUTPUT_ALL_HEADERS (#144114)

Following discussion from
https://discourse.llvm.org/t/missing-declarations-in-header-files/86678,
we decided to add a flag to output all headers. Requires #144049.

- Allows outputting all headers
- Minor whitespace change for alignment

---------

Co-authored-by: Michael Jones <michaelrj@google.com>

libc/CMakeLists.txt

@@ -135,6 +135,7 @@ endif()
 option(LLVM_LIBC_FULL_BUILD "Build and test LLVM libc as if it is the full libc" ${default_to_full_build})
 option(LLVM_LIBC_IMPLEMENTATION_DEFINED_TEST_BEHAVIOR "Build LLVM libc tests assuming our implementation-defined behavior" ON)
 option(LLVM_LIBC_ENABLE_LINTING "Enables linting of libc source files" OFF)
+option(LLVM_LIBC_ALL_HEADERS "Outputs all functions in header files, regardless of whether they are enabled on this target" OFF)
 
 option(LIBC_CONFIG_PATH "The path to user provided folder that configures the build for the target system." OFF)
 

libc/cmake/modules/LLVMLibCHeaderRules.cmake

@@ -98,7 +98,12 @@ function(add_gen_header target_name)
   set(dep_file "${out_file}.d")
   set(yaml_file ${CMAKE_SOURCE_DIR}/${ADD_GEN_HDR_YAML_FILE})
   
+  if(LLVM_LIBC_ALL_HEADERS)
+    set(entry_points "")
+  else()
     set(entry_points "${TARGET_ENTRYPOINT_NAME_LIST}")
+  endif()
+
   list(TRANSFORM entry_points PREPEND "--entry-point=")
 
   add_custom_command(

libc/test/UnitTest/CMakeLists.txt

@@ -35,7 +35,7 @@ function(add_unittest_framework_library name)
   else()
     _get_common_test_compile_options(compile_options "" "")
     target_compile_options(${name}.unit PRIVATE ${compile_options})
-endif()
+  endif()
 
   _get_hermetic_test_compile_options(compile_options "")
   target_include_directories(${name}.hermetic PRIVATE ${LIBC_INCLUDE_DIR})