Individual autoconf function broken out of acincludes.m4. This change

per the recommended style guide for autoconf and so that individual
autoconf functions can more easily be shared across projects.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16223 91177308-0d34-0410-b5e6-96231b3b80d8

autoconf/m4/link_use_r.m4

@@ -0,0 +1,23 @@
+#
+# Determine if the system can handle the -R option being passed to the linker.
+#
+# This macro is specific to LLVM.
+#
+AC_DEFUN([AC_LINK_USE_R],
+[
+  AC_MSG_CHECKING([for compiler -Wl,-R<path> option])
+  AC_LANG_SAVE
+  AC_LANG_C
+  oldcflags="$CFLAGS"
+  CFLAGS="$CFLAGS -Wl,-R."
+  AC_LINK_IFELSE([int main() { return 0; }],[ac_cv_link_use_r=yes],[ac_cv_link_use_r=no])
+  CFLAGS="$oldcflags"
+  AC_LANG_RESTORE
+  AC_MSG_RESULT($ac_cv_link_use_r)
+  if test "$ac_cv_link_use_r" = yes
+  then
+    AC_DEFINE([HAVE_LINK_R],[1],[Define if you can use -Wl,-R. to pass -R. to the linker, in order to add the current directory to the dynamic linker search path.])
+  fi
+])
+
+