switch set BOOL to option

Author: nickdesaulniers

libc/CMakeLists.txt

@@ -46,10 +46,9 @@ set(LIBC_BUILD_DIR ${CMAKE_CURRENT_BINARY_DIR})
 
 set(LIBC_ENABLE_USE_BY_CLANG OFF CACHE BOOL "Whether or not to place libc in a build directory findable by a just built clang")
 
-# LIBC_USE_HOST_KERNEL_HEADERS is brittle, and frowned upon (prefer
-# setting LIBC_KERNEL_HEADERS), but is simpler from a hello world linux host
-# build.
-set(LIBC_USE_HOST_KERNEL_HEADERS OFF CACHE BOOL "Add /usr/include to the header seach path")
+# LIBC_USE_HOST_KERNEL_HEADERS is brittle, and frowned upon (prefer setting
+# LIBC_KERNEL_HEADERS), but is simpler from a hello world linux host build.
+option(LIBC_USE_HOST_KERNEL_HEADERS "Add /usr/include to the header seach path" OFF)
 set(LIBC_KERNEL_HEADERS "" CACHE STRING "Path to Linux kernel headers")
 
 # Defining a global namespace to enclose all libc functions.