From 8decc5c726caca2381cffbd1b3585862421f5b8e Mon Sep 17 00:00:00 2001
From: Hennadii Stepanov <32963518+hebasto@users.noreply.github.com>
Date: Sun, 7 Jan 2024 11:32:51 +0000
Subject: [PATCH] build: Fix `-Xclang -internal-isystem` option

LLVM Clang >=16.0 and Apple Clang >=15.0 do not recognize
`-Xclang -internal-isystem/usr/local/include` anymore.

For example, see: https://github.com/llvm/llvm-project/commit/cbbe1d44546db52c71c9a2b18f85b87ae82df9e7
---
 configure.ac | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 7b286df6030..bcff6c79f8e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -740,7 +740,7 @@ case $host in
          dnl option to system-ify all /usr/local/include paths without adding it to the list
          dnl of search paths in case it's not already there.
          if test "$suppress_external_warnings" != "no"; then
-           AX_CHECK_PREPROC_FLAG([-Xclang -internal-isystem/usr/local/include], [CORE_CPPFLAGS="$CORE_CPPFLAGS -Xclang -internal-isystem/usr/local/include"], [], [$CXXFLAG_WERROR])
+           AX_CHECK_PREPROC_FLAG([-Xclang -internal-isystem -Xclang /usr/local/include/], [CORE_CPPFLAGS="$CORE_CPPFLAGS -Xclang -internal-isystem -Xclang /usr/local/include/"], [], [$CXXFLAG_WERROR])
          fi
 
          if test "$use_bdb" != "no" && $BREW list --versions berkeley-db@4 >/dev/null && test "$BDB_CFLAGS" = "" && test "$BDB_LIBS" = ""; then