libvpx: Pull from upstream

source/libvpx/build/make/configure.sh

 #!/bin/bash
 ##
 ##  configure.sh
 ##
 ##  This script is sourced by the main configure script and contains
 ##  utility functions and other common bits that aren't strictly libvpx
 ##  related.
 ##
 ##  This build system is based in part on the FFmpeg configure script.
 ##
@@ skipping 993 matching lines @@
 #ifndef __ILP32__
 #error "not x32"
 #endif
 EOF
         soft_enable runtime_cpu_detect
         soft_enable mmx
         soft_enable sse
         soft_enable sse2
         soft_enable sse3
         soft_enable ssse3
-        if enabled gcc && ! disabled sse4_1 && ! check_cflags -msse4; then
-            RTCD_OPTIONS="${RTCD_OPTIONS}--disable-sse4_1 "
-        else
-            soft_enable sse4_1
-        fi
 
         case  ${tgt_os} in
             win*)
                 enabled gcc && add_cflags -fno-common
                 ;;
             solaris*)
                 CC=${CC:-${CROSS}gcc}
                 CXX=${CXX:-${CROSS}g++}
                 LD=${LD:-${CROSS}gcc}
                 CROSS=${CROSS:-g}
@@ skipping 21 matching lines @@
                     *)
                         tune_cflags="-march="
                     ;;
                 esac
             ;;
             gcc*)
                 add_cflags -m${bits}
                 add_ldflags -m${bits}
                 link_with_cc=gcc
                 tune_cflags="-march="
-            setup_gnu_toolchain
+                setup_gnu_toolchain
                 #for 32 bit x86 builds, -O3 did not turn on this flag
                 enabled optimizations && check_add_cflags -fomit-frame-pointer
             ;;
             vs*)
                 # When building with Microsoft Visual Studio the assembler is
                 # invoked directly. Checking at configure time is unnecessary.
                 # Skip the check by setting AS arbitrarily
                 AS=msvs
             ;;
         esac
 
+        # We can't use 'check_cflags' until the compiler is configured and CC is
+        # populated.
+        if enabled gcc && ! disabled sse4_1 && ! check_cflags -msse4.1; then
+            RTCD_OPTIONS="${RTCD_OPTIONS}--disable-sse4_1 "
+        else
+            soft_enable sse4_1
+        fi
+
         case "${AS}" in
             auto|"")
                 which nasm >/dev/null 2>&1 && AS=nasm
                 which yasm >/dev/null 2>&1 && AS=yasm
                 [ "${AS}" = auto -o -z "${AS}" ] \
                     && die "Neither yasm nor nasm have been found"
             ;;
         esac
         log_echo "  using $AS"
         [ "${AS##*/}" = nasm ] && add_asflags -Ox
@@ skipping 197 matching lines @@
     # Prepare the PWD for building.
     for f in ${OOT_INSTALLS}; do
             install -D ${source_path}/$f $f
     done
     fi
     cp ${source_path}/build/make/Makefile .
 
     clean_temp_files
     true
 }