Bug 1880814 - Logs for libvpx configuration on various platforms r=glandium

This patch generates log files during the configuration of libvpx on
variouse platforms. These logs can be used for manual verification of
the correctness of settings. In this particular case, the log file for
win/aarch64 reveals the sve feature is disabled on win/aarch64.

The logs will be excluded to the repo, by .gitignore and .hgignore
settings.

Differential Revision: https://phabricator.services.mozilla.com/D204799

.gitignore

@@ -360,3 +360,6 @@ docs/mots/index.rst
 
 # Ignore generated directory with .class files for GeckoView annotation processor
 mobile/android/annotations/bin/
+
+# Ignore generated log files under media/libvpx
+media/libvpx/config/**/config.log

.hgignore

@@ -352,3 +352,6 @@ tps_result\.json$
 
 # Ignore generated directory with .class files for GeckoView annotation processor
 ^mobile/android/annotations/bin/
+
+# Ignore generated log files under media/libvpx
+^media/libvpx/config/.*/config.log

media/libvpx/generate_sources_mozbuild.sh

@@ -169,7 +169,8 @@ function gen_rtcd_header {
 # $1 - Header file directory.
 # $2 - Config command line.
 function gen_config_files {
-  ./configure $2 > /dev/null
+  ./configure $2 --log=$BASE_DIR/$LIBVPX_CONFIG_DIR/$1/config.log > /dev/null
+  echo "Log file: $BASE_DIR/$LIBVPX_CONFIG_DIR/$1/config.log"
 
   # Disable HAVE_UNISTD_H.
   ( echo '/HAVE_UNISTD_H'; echo 'd' ; echo 'w' ; echo 'q' ) | ed -s vpx_config.h