* configure.ac: Detect xcrun on OSX and use it for make, gcc and libxml.

ChangeLog

+2013-12-27  Jan Djärv  <jan.h.d@swipnet.se>
+
+	* configure.ac: Detect xcrun on OSX and use it for make, gcc and
+	libxml.
+
 2013-12-26  Paul Eggert  <eggert@cs.ucla.edu>
 
 	Fix core dumps with gcc -fsanitize=address and GNU/Linux.

configure.ac

@@ -39,6 +39,18 @@ then
   esac
 fi
 
+case "`uname 2>/dev/null`" in
+ *Darwin*)
+  xcsdkdir=
+  AC_CHECK_PROGS(XCRUN, [xcrun])
+  if test x"$XCRUN" != x; then
+    AC_CHECK_PROGS(MAKE, [make "$XCRUN make"])
+    export MAKE
+    xcsdkdir="`$XCRUN --show-sdk-path 2>/dev/null`"
+  fi
+  ;;
+esac
+
 dnl Set emacs_config_options to the options of 'configure', quoted for the shell,
 dnl and then quoted again for a C string.  Separate options with spaces.
 dnl Add some environment variables, if they were passed via the environment
@@ -638,7 +650,13 @@ fi
 #### Choose a compiler.
 
 dnl Sets GCC=yes if using gcc.
-AC_PROG_CC
+if test x$opsys = xdarwin && test x"$XCRUN" != x; then
+  AC_PROG_CC([gcc cc cl clang "$XCRUN gcc" "$XCRUN clang"])
+  AC_CHECK_PROGS(AR, [ar "$XCRUN ar"])
+  test x"$AR" != x && export AR
+else
+  AC_PROG_CC
+fi
 AM_PROG_CC_C_O
 
 if test x$GCC = xyes; then
@@ -3275,14 +3293,14 @@ if test "${with_xml2}" != "no"; then
   # Built-in libxml2 on OS X 10.8 lacks libxml-2.0.pc.
   if test "${HAVE_LIBXML2}" != "yes" -a "$opsys" = "darwin"; then
     SAVE_CPPFLAGS="$CPPFLAGS"
-    CPPFLAGS="$CPPFLAGS -I/usr/include/libxml2"
+    CPPFLAGS="$CPPFLAGS -I$xcsdkdir/usr/include/libxml2"
     AC_CHECK_HEADER(libxml/HTMLparser.h,
       [AC_CHECK_DECL(HTML_PARSE_RECOVER, HAVE_LIBXML2=yes, ,
       		     [#include <libxml/HTMLparser.h>])])
     CPPFLAGS="$SAVE_CPPFLAGS"
     if test "${HAVE_LIBXML2}" = "yes"; then
+      LIBXML2_CFLAGS="-I'$xcsdkdir/usr/include/libxml2'"
       LIBXML2_LIBS="-lxml2"
-      LIBXML2_CFLAGS="-I/usr/include/libxml2"
     fi
   fi
   if test "${HAVE_LIBXML2}" = "yes"; then