libvpx: Pull from upstream

source/libvpx/configure

 #!/bin/bash
 ##
 ##  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 637 matching lines @@
         ;;
     esac
 
     # Other toolchain specific defaults
     case $toolchain in x86*|ppc*|universal*) soft_enable postproc;; esac
 
     if enabled postproc_visualizer; then
         enabled postproc || die "postproc_visualizer requires postproc to be enabled"
     fi
 
-    # Enable unit tests if we have a working C++ compiler
+    # Enable unit tests by default if we have a working C++ compiler.
     case "$toolchain" in
         *-vs*)
             soft_enable unit_tests
         ;;
         *-android-*)
             # GTestLog must be modified to use Android logging utilities.
         ;;
         *-darwin-*)
             # iOS/ARM builds do not work with gtest. This does not match
             # x86 targets.
         ;;
         *)
-            check_cxx "$@" <<EOF && soft_enable unit_tests
+            enabled pthread_h && check_cxx "$@" <<EOF && soft_enable unit_tests
 int z;
 EOF
         ;;
     esac
 }
 
 
 ##
 ## END APPLICATION SPECIFIC CONFIGURATION
 ##
 CONFIGURE_ARGS="$@"
 process "$@"
 print_webm_license ${BUILD_PFX}vpx_config.c "/*" " */"
 cat <<EOF >> ${BUILD_PFX}vpx_config.c
 static const char* const cfg = "$CONFIGURE_ARGS";
 const char *vpx_codec_build_config(void) {return cfg;}
 EOF