Only run an unbridled parallel make (make -j) if MAKEFLAGS is unset

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/scripts/basic-build-test.sh b/tests/scripts/basic-build-test.sh
index 83aa87a..4b05d1b 100755
--- a/tests/scripts/basic-build-test.sh
+++ b/tests/scripts/basic-build-test.sh
@@ -62,6 +62,11 @@
 : ${SEED:=1}
 export SEED
 
+# if MAKEFLAGS is not set add the -j option to speed up invocations of make
+if [ -z "${MAKEFLAGS+set}" ]; then
+    export MAKEFLAGS="-j"
+fi
+
 # To avoid setting OpenSSL and GnuTLS for each call to compat.sh and ssl-opt.sh
 # we just export the variables they require
 export OPENSSL_CMD="$OPENSSL"
@@ -87,7 +92,7 @@
 make clean
 cp "$CONFIG_H" "$CONFIG_BAK"
 scripts/config.py full
-make -j
+make
 
 
 # Step 2 - Execute the tests