fix: include resource directory in search path for include resolution

This is an issue with more recent SDKs (observed from Xcode 15.3 15E204a
shipped SDKs onwards) and explicit inclusion resolves it. We have to use
`:=` to force immediate resolution.

Author: kwvg

depends/hosts/darwin.mk

@@ -13,8 +13,10 @@ OSX_SDK=$(SDK_PATH)/Xcode-$(XCODE_VERSION)-$(XCODE_BUILD_ID)-extracted-SDK-with-
 # distro releases.
 #
 # Source: https://lists.gnu.org/archive/html/bug-make/2017-11/msg00017.html
-clang_prog=$(shell $(SHELL) $(.SHELLFLAGS) "command -v clang")
-clangxx_prog=$(shell $(SHELL) $(.SHELLFLAGS) "command -v clang++")
+clang_prog:=$(shell $(SHELL) $(.SHELLFLAGS) "command -v clang")
+clangxx_prog:=$(shell $(SHELL) $(.SHELLFLAGS) "command -v clang++")
+
+clang_resource_dir:=$(shell $(SHELL) $(.SHELLFLAGS) "$(clang_prog) -print-resource-dir")
 
 darwin_AR=$(shell $(SHELL) $(.SHELLFLAGS) "command -v llvm-ar")
 darwin_DSYMUTIL=$(shell $(SHELL) $(.SHELLFLAGS) "command -v dsymutil")
@@ -52,12 +54,14 @@ darwin_STRIP=$(shell $(SHELL) $(.SHELLFLAGS) "command -v llvm-strip")
 #         non-determinism issues with the Identifier field.
 
 darwin_CC=env -u C_INCLUDE_PATH -u CPLUS_INCLUDE_PATH $(clang_prog) --target=$(host) \
-              -isysroot$(OSX_SDK) -nostdlibinc \
+              -isysroot$(OSX_SDK) -nostdinc \
+              -isystem$(clang_resource_dir)/include \
               -iwithsysroot/usr/include -iframeworkwithsysroot/System/Library/Frameworks
 
 darwin_CXX=env -u C_INCLUDE_PATH -u CPLUS_INCLUDE_PATH $(clangxx_prog) --target=$(host) \
-               -isysroot$(OSX_SDK) -nostdlibinc \
+               -isysroot$(OSX_SDK) -nostdinc -nostdinc++ \
                -iwithsysroot/usr/include/c++/v1 \
+               -isystem$(clang_resource_dir)/include \
                -iwithsysroot/usr/include -iframeworkwithsysroot/System/Library/Frameworks
 
 darwin_CFLAGS=-pipe -std=$(C_STANDARD) -mmacos-version-min=$(OSX_MIN_VERSION)