Add aom_ports arm support to the cmake build.

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

Change-Id: Ib1c5e04134911fd7ccdcb014b53a06e856368a5d
diff --git a/aom_ports/aom_ports.cmake b/aom_ports/aom_ports.cmake
index 5f67eab..3e8883d 100644
--- a/aom_ports/aom_ports.cmake
+++ b/aom_ports/aom_ports.cmake
@@ -24,7 +24,11 @@
 
 set(AOM_PORTS_ASM_MMX "${AOM_ROOT}/aom_ports/emms.asm")
 
-# For targets where HAVE_MMX is true:
+set(AOM_PORTS_SOURCES_ARM
+    "${AOM_ROOT}/aom_ports/arm.h"
+    "${AOM_ROOT}/aom_ports/arm_cpudetect.c")
+
+# For arm targets and targets where HAVE_MMX is true:
 #   Creates the aom_ports build target, adds the includes in aom_ports to the
 #   target, and makes libaom depend on it.
 # Otherwise:
@@ -35,6 +39,11 @@
   if (HAVE_MMX)
     add_asm_library("aom_ports" "AOM_PORTS_ASM_MMX" "aom")
     set(aom_ports_has_symbols 1)
+  elseif ("${AOM_TARGET_CPU}" MATCHES "arm")
+    add_library(aom_ports OBJECT ${AOM_PORTS_SOURCES_ARM})
+    set(aom_ports_has_symbols 1)
+    list(APPEND AOM_LIB_TARGETS aom_ports)
+    target_sources(aom PRIVATE $<TARGET_OBJECTS:aom_ports>)
   endif ()
 
   if (aom_ports_has_symbols)
diff --git a/build/cmake/toolchains/armv7s-ios.cmake b/build/cmake/toolchains/armv7s-ios.cmake
index 5e07b21..b6b403b 100644
--- a/build/cmake/toolchains/armv7s-ios.cmake
+++ b/build/cmake/toolchains/armv7s-ios.cmake
@@ -33,6 +33,9 @@
 # No intrinsics flag required for armv7s-ios.
 set(AOM_NEON_INTRIN_FLAG "")
 
+# No runtime cpu detect for armv7s-ios.
+set(CONFIG_RUNTIME_CPU_DETECT 0 CACHE BOOL "")
+
 # Assembler sources must be converted for ARM iOS targets.
 set(AOM_ADS2GAS_REQUIRED 1)
 set(AOM_ADS2GAS "${CMAKE_CURRENT_SOURCE_DIR}/build/make/ads2gas_apple.pl")