try to reuse ffmpeg config for linux on other *nix

ffmpeg.gyp

Index: ffmpeg.gyp
===================================================================
--- ffmpeg.gyp	(revision 60551)
+++ ffmpeg.gyp	(working copy)
@@ -61,6 +61,11 @@
       ['target_arch=="arm"', {
         'ffmpeg_asm_lib': 0,
       }],
+      ['OS=="mac" or OS=="win"', {
+        'os_config%': '<(OS)',
+      }, {  # all other Unix OS's use the linux config 
+        'os_config%': 'linux',
+      }],
 
       # libvpx location.
       # TODO(scherkus): libvpx_hack_dir is a hack to make -L work on linux.
@@ -165,11 +170,11 @@
             'patched-ffmpeg-mt/libavutil/mem.c',
             'patched-ffmpeg-mt/libavutil/pixdesc.c',
             'patched-ffmpeg-mt/libavutil/rational.c',
-            'config/<(ffmpeg_branding)/<(OS)/<(ffmpeg_config)/config.h',
+            'config/<(ffmpeg_branding)/<(os_config)/<(ffmpeg_config)/config.h',
             'config/libavutil/avconfig.h',
           ],
           'include_dirs': [
-            'config/<(ffmpeg_branding)/<(OS)/<(ffmpeg_config)',
+            'config/<(ffmpeg_branding)/<(os_config)/<(ffmpeg_config)',
             'patched-ffmpeg-mt',
             'config',
           ],
@@ -421,6 +426,11 @@
                     'ldflags': [
                       '-L<(libvpx_hack_dir)/lib/<(OS)/<(target_arch)',
                     ],
+                  }, {
+                    # Using libvpx provided by the system.
+                    'ldflags': [
+                      '-L/usr/local/lib',

[scherkus (not reviewing), 2010/10/14 19:03:42]

shouldn't this already be in the path?

use_system_vpx just uses -lvpx and assumes that its in your default path

[ruben, 2010/10/14 19:11:35]

Yes, I was surprised it wasn't also, but how would that path get pulled in for
ffmpeg exactly?  ffmpeg.gyp doesn't call any of the pkg-config targets from
build/linux/system.gyp, nor does it invoke pkg-config itself for the flags for
libvpx.  On FreeBSD, that caused a linking failure: has the use_system_vpx flag
been tested on linux?

[scherkus (not reviewing), 2010/10/14 19:40:48]

I think when libvpx was first released they didn't offer a pkg-config (see
comment at top for use_system_vpx)

I'd fine using a pkg-config line similar to use_system_ffmpeg for CFLAGS

+                    ],
                   }],
                 ],
               },