tools: zstd: override max safe compression level

ZTSD limits the safe compression level to a max of 19 as 20 to 22 cause
increased RAM usage. Higher levels require --ultra arg passed.

There isn't currently a way to set --ultra using ENV options similar to
ZSTD_CLEVEL and ZSTD_CLEVEL is limited to 19.

To fix this, we can increase the max safe compression level by providing
a custom ZSTDCLI_CLEVEL_MAX value with CFLAGS.

The max safe level is increased to 20.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>

tools/zstd/Makefile

@@ -17,6 +17,9 @@ include $(INCLUDE_DIR)/host-build.mk
 
 HOSTCC:= $(HOSTCC_NOCACHE)
 
+HOST_CFLAGS += \
+	-DZSTDCLI_CLEVEL_MAX=20
+
 HOST_MAKE_FLAGS += \
 	ZSTD_LEGACY_SUPPORT=7 \
 	BACKTRACE=0 \