arm_cpudetect.c: replace configure option w/cmake

--disable-runtime-cpu-detect -> -DCONFIG_RUNTIME_CPU_DETECT=0

Change-Id: I347d5de13c60c01e435230c9dba6435a39312ea0

aom_ports/arm_cpudetect.c

diff --git a/aom_ports/arm_cpudetect.c b/aom_ports/arm_cpudetect.c
index 5a75bb3..1696f15 100644
--- a/aom_ports/arm_cpudetect.c
+++ b/aom_ports/arm_cpudetect.c
@@ -145,6 +145,6 @@
 }
 #else  /* end __linux__ */
 #error \
-    "--enable-runtime-cpu-detect selected, but no CPU detection method " \
-"available for your platform. Reconfigure with --disable-runtime-cpu-detect."
+    "Runtime CPU detection selected, but no CPU detection method " \
+"available for your platform. Rerun cmake with -DCONFIG_RUNTIME_CPU_DETECT=0."
 #endif