[libc] Fix defaulting the full build

Summary:
This was missing the architecture macros as they were defined just
below.

Author: jhuber6

libc/CMakeLists.txt

@@ -128,6 +128,10 @@ else()
   endif()
 endif()
 
+# Defines LIBC_TARGET_ARCHITECTURE and associated macros.
+set(LIBC_TARGET_TRIPLE "" CACHE STRING "The target triple for the libc build.")
+include(LLVMLibCArchitectures)
+
 # Some targets can only support the full build.
 set(default_to_full_build OFF)
 if(LIBC_TARGET_OS_IS_GPU)
@@ -138,16 +142,11 @@ option(LLVM_LIBC_FULL_BUILD "Build and test LLVM libc as if it is the full libc"
 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)
 
-set(LIBC_TARGET_TRIPLE "" CACHE STRING "The target triple for the libc build.")
-
 option(LIBC_CONFIG_PATH "The path to user provided folder that configures the build for the target system." OFF)
 
 set(LIBC_ENABLE_UNITTESTS ON)
 set(LIBC_ENABLE_HERMETIC_TESTS ${LLVM_LIBC_FULL_BUILD})
 
-# Defines LIBC_TARGET_ARCHITECTURE and associated macros.
-include(LLVMLibCArchitectures)
-
 set(LIBC_CONFIG_JSON_FILE_LIST "")
 
 if(NOT LIBC_CONFIG_PATH)