Fix VP9 build setup

Update configuration script to use an external build, so we can remove use of
isysroot which is broken in the latest NDK r19c. Also switch from gnustl_static
to c++_static so that ndk-build with NDK r19c succeeds.

Issue: #5922
PiperOrigin-RevId: 250287551

extensions/vp9/README.md

@@ -29,6 +29,7 @@ VP9_EXT_PATH="${EXOPLAYER_ROOT}/extensions/vp9/src/main"
 ```
 
 * Download the [Android NDK][] and set its location in an environment variable.
+  The build configuration has been tested with Android NDK r19c.
 
 ```
 NDK_PATH="<path to Android NDK>"
@@ -54,7 +55,7 @@ git checkout tags/v1.8.0 -b v1.8.0
 
 ```
 cd ${VP9_EXT_PATH}/jni && \
-./generate_libvpx_android_configs.sh "${NDK_PATH}"
+./generate_libvpx_android_configs.sh
 ```
 
 * Build the JNI native libraries from the command line:

extensions/vp9/src/main/jni/Application.mk

@@ -15,6 +15,6 @@
 #
 
 APP_OPTIM := release
-APP_STL := gnustl_static
+APP_STL := c++_static
 APP_CPPFLAGS := -frtti
-APP_PLATFORM := android-9
+APP_PLATFORM := android-16

extensions/vp9/src/main/jni/generate_libvpx_android_configs.sh

@@ -20,46 +20,33 @@
 
 set -e
 
-if [ $# -ne 1 ]; then
-  echo "Usage: ${0} <path_to_android_ndk>"
+if [ $# -ne 0 ]; then
+  echo "Usage: ${0}"
   exit
 fi
 
-ndk="${1}"
-shift 1
-
 # configuration parameters common to all architectures
 common_params="--disable-examples --disable-docs --enable-realtime-only"
 common_params+=" --disable-vp8 --disable-vp9-encoder --disable-webm-io"
 common_params+=" --disable-libyuv --disable-runtime-cpu-detect"
+common_params+=" --enable-external-build"
 
 # configuration parameters for various architectures
 arch[0]="armeabi-v7a"
-config[0]="--target=armv7-android-gcc --sdk-path=$ndk --enable-neon"
-config[0]+=" --enable-neon-asm"
+config[0]="--target=armv7-android-gcc --enable-neon --enable-neon-asm"
 
-arch[1]="armeabi"
-config[1]="--target=armv7-android-gcc --sdk-path=$ndk --disable-neon"
-config[1]+=" --disable-neon-asm"
+arch[1]="x86"
+config[1]="--force-target=x86-android-gcc --disable-sse2"
+config[1]+=" --disable-sse3 --disable-ssse3 --disable-sse4_1 --disable-avx"
+config[1]+=" --disable-avx2 --enable-pic"
 
-arch[2]="mips"
-config[2]="--force-target=mips32-android-gcc --sdk-path=$ndk"
+arch[2]="arm64-v8a"
+config[2]="--force-target=armv8-android-gcc --enable-neon"
 
-arch[3]="x86"
-config[3]="--force-target=x86-android-gcc --sdk-path=$ndk --disable-sse2"
+arch[3]="x86_64"
+config[3]="--force-target=x86_64-android-gcc --disable-sse2"
 config[3]+=" --disable-sse3 --disable-ssse3 --disable-sse4_1 --disable-avx"
-config[3]+=" --disable-avx2 --enable-pic"
-
-arch[4]="arm64-v8a"
-config[4]="--force-target=armv8-android-gcc --sdk-path=$ndk --enable-neon"
-
-arch[5]="x86_64"
-config[5]="--force-target=x86_64-android-gcc --sdk-path=$ndk --disable-sse2"
-config[5]+=" --disable-sse3 --disable-ssse3 --disable-sse4_1 --disable-avx"
-config[5]+=" --disable-avx2 --enable-pic --disable-neon --disable-neon-asm"
-
-arch[6]="mips64"
-config[6]="--force-target=mips64-android-gcc --sdk-path=$ndk"
+config[3]+=" --disable-avx2 --enable-pic --disable-neon --disable-neon-asm"
 
 limit=$((${#arch[@]} - 1))
 
@@ -102,10 +89,7 @@ for i in $(seq 0 ${limit}); do
   # configure and make
   echo "build_android_configs: "
   echo "configure ${config[${i}]} ${common_params}"
-  ../../libvpx/configure ${config[${i}]} ${common_params} --extra-cflags=" \
-    -isystem $ndk/sysroot/usr/include/arm-linux-androideabi \
-    -isystem $ndk/sysroot/usr/include \
-    "
+  ../../libvpx/configure ${config[${i}]} ${common_params}
   rm -f libvpx_srcs.txt
   for f in ${allowed_files}; do
     # the build system supports multiple different configurations. avoid