Set meaningful test configuration names when running tests

Set MBEDTLS_TEST_PLATFORM and MBEDTLS_TEST_CONFIGURATION to meaningful
values in all.sh. These environment variables are used when
writing an outcome file, which happens if MBEDTLS_TEST_OUTCOME_FILE is
also set.

When running one of the try-multiple-configuration scripts, set
MBEDTLS_TEST_CONFIGURATION to a value that uniquely describes the
configuration.
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index c7bf428..a97189a 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -121,6 +121,9 @@
     FORCE=0
     KEEP_GOING=0
 
+    : ${MBEDTLS_TEST_PLATFORM="$(uname -s | tr -c \\n0-9A-Za-z _)-$(uname -m | tr -c \\n0-9A-Za-z _)"}
+    export MBEDTLS_TEST_PLATFORM
+
     # Default commands, can be overridden by the environment
     : ${OPENSSL:="openssl"}
     : ${OPENSSL_LEGACY:="$OPENSSL"}
@@ -1424,6 +1427,7 @@
     # The cleanup function will restore it.
     cp -p "$CONFIG_H" "$CONFIG_BAK"
     current_component="$1"
+    export MBEDTLS_TEST_CONFIGURATION="$current_component"
     "$@"
     cleanup
 }