[build] Add missing checks to libvpx build system for macOS 11.

libs/libvpx/build/make/configure.sh

@@ -807,6 +807,10 @@ process_common_toolchain() {
         tgt_isa=x86_64
         tgt_os=darwin19
         ;;
+      *darwin20*)
+        tgt_isa=x86_64
+        tgt_os=darwin20
+        ;;
       x86_64*mingw32*)
         tgt_os=win64
         ;;

libs/libvpx/build/make/iosbuild.sh

@@ -35,8 +35,8 @@ ARM_TARGETS="arm64-darwin-gcc
              armv7s-darwin-gcc"
 SIM_TARGETS="x86-iphonesimulator-gcc
              x86_64-iphonesimulator-gcc"
-OSX_TARGETS="x86-darwin18-gcc
-             x86_64-darwin18-gcc"
+OSX_TARGETS="x86-darwin20-gcc
+             x86_64-darwin20-gcc"
 TARGETS="${ARM_TARGETS} ${SIM_TARGETS}"
 
 # Configures for the target specified by $1, and invokes make with the dist
@@ -272,7 +272,7 @@ cat << EOF
     --help: Display this message and exit.
     --enable-shared: Build a dynamic framework for use on iOS 8 or later.
     --extra-configure-args <args>: Extra args to pass when configuring libvpx.
-    --macosx: Uses darwin18 targets instead of iphonesimulator targets for x86
+    --macosx: Uses darwin20 targets instead of iphonesimulator targets for x86
               and x86_64. Allows linking to framework when builds target MacOSX
               instead of iOS.
     --preserve-build-output: Do not delete the build directory.

libs/libvpx/configure

@@ -150,6 +150,7 @@ all_platforms="${all_platforms} x86_64-darwin16-gcc"
 all_platforms="${all_platforms} x86_64-darwin17-gcc"
 all_platforms="${all_platforms} x86_64-darwin18-gcc"
 all_platforms="${all_platforms} x86_64-darwin19-gcc"
+all_platforms="${all_platforms} x86_64-darwin20-gcc"
 all_platforms="${all_platforms} x86_64-iphonesimulator-gcc"
 all_platforms="${all_platforms} x86_64-linux-gcc"
 all_platforms="${all_platforms} x86_64-linux-icc"