Fix generic-gnu target build

Added macro to conditionally compile some of the
post-processing functions only when CONFIG_POSTPROC
is defined.

This was causing the build for the generic-gnu target
to fail.

Change-Id: Ibfa447feceb7a0528135025f105be48f97e9965c

vp8/common/postproc.c

diff --git a/vp8/common/postproc.c b/vp8/common/postproc.c
index 7d0fbf6..8e546d5 100644
--- a/vp8/common/postproc.c
+++ b/vp8/common/postproc.c
@@ -310,6 +310,7 @@
     }
 }
 
+#if CONFIG_POSTPROC
 static void vp8_de_mblock(YV12_BUFFER_CONFIG         *post,
                           int                         q)
 {
@@ -382,6 +383,7 @@
         vp8_yv12_copy_frame(source, post);
     }
 }
+#endif
 
 #if !(CONFIG_TEMPORAL_DENOISING)
 void vp8_de_noise(VP8_COMMON                 *cm,

vp8/encoder/onyx_if.c

diff --git a/vp8/encoder/onyx_if.c b/vp8/encoder/onyx_if.c
index 560134e..e95e44f 100644
--- a/vp8/encoder/onyx_if.c
+++ b/vp8/encoder/onyx_if.c
@@ -5227,7 +5227,7 @@
                 int y_samples = orig->y_height * orig->y_width ;
                 int uv_samples = orig->uv_height * orig->uv_width ;
                 int t_samples = y_samples + 2 * uv_samples;
-                double sq_error, sq_error2;
+                double sq_error;
 
                 ye = calc_plane_error(orig->y_buffer, orig->y_stride,
                   recon->y_buffer, recon->y_stride, orig->y_width, orig->y_height);
@@ -5250,6 +5250,7 @@
 #if CONFIG_POSTPROC
                 {
                     YV12_BUFFER_CONFIG      *pp = &cm->post_proc_buffer;
+                    double sq_error2;
                     double frame_psnr2, frame_ssim2 = 0;
                     double weight = 0;