CI: Work around problem with running the initial 'make clean' in parallel (#18)

    Just don't pass '-j' to the 'make clean' command

tools/ci/build_examples.sh

@@ -114,11 +114,11 @@ build_example () {
         # build non-verbose first
         local BUILDLOG=$(mktemp -t examplebuild.XXXX.log)
         (
-            make clean defconfig &> >(tee -a "${BUILDLOG}") &&
+            MAKEFLAGS= make clean defconfig &> >(tee -a "${BUILDLOG}") &&
             make all &> >(tee -a "${BUILDLOG}")
         ) || {
             RESULT=$?; FAILED_EXAMPLES+=" ${EXAMPLE_NAME}"
-            make V=1 clean defconfig && make V=1 # verbose output for errors
+            make MAKEFLAGS= V=1 clean defconfig && make V=1 # verbose output for errors
         }
     popd
 

tools/ci/test_build_system.sh

@@ -49,7 +49,7 @@ function run_tests()
     make defconfig || exit $?
 
     print_status "Try to clean fresh directory..."
-    make clean || exit $?
+    MAKEFLAGS= make clean || exit $?
 
     BOOTLOADER_BINS="bootloader/bootloader.elf bootloader/bootloader.bin"
     APP_BINS="app-template.elf app-template.bin"