c3: fix c3 build scripts issue. [1/1]

PD#SWPL-97754

Problem:
Cache files causing compilation issues.

Solution:
delete cache files.

Verify:
N/A.

Change-Id: Ifced55061ea102418b16dd3e57dbd9c82e7fee0f
Signed-off-by: shijie.xiong <shijie.xiong@amlogic.com>
diff --git a/c3_fastboot.sh b/c3_fastboot.sh
index f68f0f7..02f38f5 100755
--- a/c3_fastboot.sh
+++ b/c3_fastboot.sh
@@ -18,6 +18,8 @@
 	UBOOT_DIR=$2
 fi
 
+#Clear cache files
+[ -d $RTOS_BASE_DIR/output ] && rm -rf $RTOS_BASE_DIR/output
 #Get the current project environment variables
 source $RTOS_BASE_DIR/scripts/env.sh arm64 c3 aw419_c308l fastboot