Add support for CONFIG_FILTER_INTRA to the cmake build.

Note: CONFIG_FILTER_INTRA is broken in both build systems due
to link errors. This is a parity patch.

BUG=https://bugs.chromium.org/p/aomedia/issues/detail?id=76

Change-Id: I713bc7b6f5f13387bbf6b9e3df22731c22d558cc

av1/av1.cmake

@@ -173,13 +173,17 @@ set(AOM_AV1_COMMON_SSSE3_INTRIN
     "${AOM_ROOT}/av1/common/x86/av1_convolve_ssse3.c")
 
 set(AOM_AV1_COMMON_SSE4_1_INTRIN
-    # Requires CONFIG_FILTER_INTRA
-    #"${AOM_ROOT}/av1/common/x86/filterintra_sse4.c"
     # Requires CONFIG_CDEF
     #"${AOM_ROOT}/av1/common/x86/od_dering_sse4.c"
     "${AOM_ROOT}/av1/common/x86/av1_fwd_txfm1d_sse4.c"
     "${AOM_ROOT}/av1/common/x86/av1_fwd_txfm2d_sse4.c")
 
+if (CONFIG_FILTER_INTRA)
+  set(AOM_AV1_COMMON_SSE4_1_INTRIN
+      ${AOM_AV1_COMMON_SSE4_1_INTRIN}
+      "${AOM_ROOT}/av1/common/x86/filterintra_sse4.c")
+endif ()
+
 set(AOM_AV1_COMMON_AVX2_INTRIN
     "${AOM_ROOT}/av1/common/x86/hybrid_inv_txfm_avx2.c")