Expand cmake rtcd support to support disabling simd flavors.

Required to build for arm targets that lack media (armv6) support.

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

Change-Id: I5c53e413a2eaa4f753ff4163be185ba9255f6661

build/cmake/aom_configure.cmake

diff --git a/build/cmake/aom_configure.cmake b/build/cmake/aom_configure.cmake
index 49b06c7..1afae34 100644
--- a/build/cmake/aom_configure.cmake
+++ b/build/cmake/aom_configure.cmake
@@ -248,7 +248,7 @@
   list(GET AOM_RTCD_SYMBOL_LIST ${NUM} AOM_RTCD_SYMBOL)
   execute_process(
     COMMAND ${PERL_EXECUTABLE} "${AOM_ROOT}/build/make/rtcd.pl"
-      --arch=${AOM_ARCH} --sym=${AOM_RTCD_SYMBOL}
+      --arch=${AOM_ARCH} --sym=${AOM_RTCD_SYMBOL} ${AOM_RTCD_FLAGS}
       --config=${AOM_CONFIG_DIR}/${AOM_ARCH}.rtcd ${AOM_RTCD_CONFIG_FILE}
     OUTPUT_FILE ${AOM_RTCD_HEADER_FILE})
 endforeach()
@@ -258,7 +258,8 @@
     OUTPUT ${output}
     COMMAND ${PERL_EXECUTABLE}
     ARGS "${AOM_ROOT}/build/make/rtcd.pl" --arch=${AOM_ARCH} --sym=${symbol}
-      --config=${AOM_CONFIG_DIR}/${AOM_ARCH}.rtcd ${config} > ${output}
+      ${AOM_RTCD_FLAGS} --config=${AOM_CONFIG_DIR}/${AOM_ARCH}.rtcd ${config}
+      > ${output}
     DEPENDS ${config}
     COMMENT "Generating ${output}"
     WORKING_DIRECTORY ${AOM_CONFIG_DIR}

build/cmake/toolchains/armv7s-ios.cmake

diff --git a/build/cmake/toolchains/armv7s-ios.cmake b/build/cmake/toolchains/armv7s-ios.cmake
index b6b403b..a81f5ae 100644
--- a/build/cmake/toolchains/armv7s-ios.cmake
+++ b/build/cmake/toolchains/armv7s-ios.cmake
@@ -41,4 +41,8 @@
 set(AOM_ADS2GAS "${CMAKE_CURRENT_SOURCE_DIR}/build/make/ads2gas_apple.pl")
 set(AOM_GAS_EXT "S")
 
+# RTCD generation requires --disable-media for armv7s-ios.
+set(AOM_RTCD_FLAGS ${AOM_RTCD_FLAGS} --disable-media)
+string(STRIP AOM_RTCD_FLAGS ${AOM_RTCD_FLAGS})
+
 endif ()  # AOM_BUILD_CMAKE_ARMV7S_IOS_CMAKE_