libvpx: Pull from upstream

source/libvpx/configure

 #!/bin/sh
 ##
 ##  configure
 ##
 ##  This script is the front-end to the build system. It provides a similar
 ##  interface to standard configure scripts with some extra bits for dealing
 ##  with toolchains that differ from the standard POSIX interface and
 ##  for extracting subsets of the source tree. In theory, reusable parts
 ##  of this script were intended to live in build/make/configure.sh,
 ##  but in practice, the line is pretty blurry.
@@ skipping 476 matching lines @@
         fi
     done
 
 }
 
 process_detect() {
     if enabled shared; then
         # Can only build shared libs on a subset of platforms. Doing this check
         # here rather than at option parse time because the target auto-detect
         # magic happens after the command line has been parsed.
-        if ! enabled linux; then
+        if ! enabled linux && ! enabled os2; then
             if enabled gnu; then
                 echo "--enable-shared is only supported on ELF; assuming this is OK"
             else
-                die "--enable-shared only supported on ELF for now"
+                die "--enable-shared only supported on ELF and OS/2 for now"
             fi
         fi
     fi
     if [ -z "$CC" ] || enabled external_build; then
         echo "Bypassing toolchain for environment detection."
         enable_feature external_build
         check_header() {
             log fake_check_header "$@"
             header=$1
             shift
@@ skipping 199 matching lines @@
 ## END APPLICATION SPECIFIC CONFIGURATION
 ##
 CONFIGURE_ARGS="$@"
 process "$@"
 print_webm_license ${BUILD_PFX}vpx_config.c "/*" " */"
 cat <<EOF >> ${BUILD_PFX}vpx_config.c
 #include "vpx/vpx_codec.h"
 static const char* const cfg = "$CONFIGURE_ARGS";
 const char *vpx_codec_build_config(void) {return cfg;}
 EOF