autotools: make it possible to forcibly disable neon.

configure.ac

@@ -477,6 +477,17 @@ build_cpu_sse3="no"
 build_cpu_altivec="no"
 build_cpu_neon="no"
 
+want_neon="yes"
+AC_ARG_ENABLE([neon],
+   [AC_HELP_STRING([--disable-neon], [disable neon support @<:@default=enable@:>@])],
+   [
+    if test "x${enableval}" = "xyes"; then
+       want_neon="yes"
+    else
+       want_neon="no"
+    fi
+   ])
+
 SSE3_CFLAGS=""
 ALTIVEC_CFLAGS=""
 NEON_CFLAGS=""
@@ -541,6 +552,7 @@ case $host_cpu in
     fi
     ;;
   arm*)
+    if test "x${want_neon}" = "xyes"; then
        build_cpu_neon="yes"
        AC_MSG_CHECKING([whether to use NEON instructions])
        CFLAGS_save="${CFLAGS}"
@@ -558,6 +570,7 @@ case $host_cpu in
            build_cpu_neon="no"
        	 ])
        CFLAGS="${CFLAGS_save}"
+    fi
     ;;
 esac