build: support darwin targets

Mac OS X now uses the llvm linker, so our --gc-sections logic is not
supported. Furthermore, linker-scripts aren't supported either. Add GNU-ld
and Darwin detection and drop any GNU-ld specific options if not
supported.

Dropping --gc-sections and its related options is fine. We will produce
bigger binaries, but that's just what you get if you don't support that.
On Darwin we try the -dead_stip options instead. They should work
sufficiently well.

Regarding version-scripts, we still set visibility=hidden by default and
require compilers to support __attribute__((__visibility__("public"))). So
symbols are correctly exported, but version-information will be lost.
Again, that's an issue of the target architecture and we don't care
whether they lack useful features.

(extended commit-msg and reorder am-conditionals)
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/configure.ac b/configure.ac
index 4373b92..9b4d02f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -117,6 +117,25 @@ AM_CONDITIONAL([BUILD_ENABLE_OPTIMIZATIONS],
                [test "x$enable_optimizations" = "xyes"])
 
 #
+# Check which linker is used
+#
+
+AM_CONDITIONAL([BUILD_HAVE_GNU_LD],
+               [test "x$with_gnu_ld" = "xyes"])
+
+#
+# Detect darwin targets
+#
+
+case "$host_os" in
+  darwin*)
+    $is_darwin = "xyes";;
+esac
+
+AM_CONDITIONAL([BUILD_IS_DARWIN],
+               [test "x$is_darwin" = "xyes"])
+
+#
 # Makefile vars
 # After everything is configured, we create all makefiles.
 #
@@ -137,6 +156,7 @@ AC_MSG_NOTICE([Build configuration:
           exec-prefix: $exec_prefix
                libdir: $libdir
            includedir: $includedir
+              host-os: $host_os
 
   Miscellaneous Options:
                 debug: $enable_debug