perf: disable shellcheck

Since upstream commit:
b809fc656e763296f227b9b31e8f225e5977a8af ("perf build: Shellcheck support
for OUTPUT directory")

perf will attempt to run shellcheck on the test shell scripts, however
there is no point in doing this in OpenWrt and while perf checks for
shellcheck presence on your host it can fail to build in some cases.

So, simply disable it for now.

Link: https://github.com/openwrt/openwrt/pull/19361
Signed-off-by: Robert Marko <robimarko@gmail.com>

package/devel/perf/Makefile

@@ -10,7 +10,7 @@ include $(INCLUDE_DIR)/kernel.mk
 
 PKG_NAME:=perf
 PKG_VERSION:=$(LINUX_VERSION)
-PKG_RELEASE:=6
+PKG_RELEASE:=7
 
 PKG_BUILD_FLAGS:=no-mips16 no-lto
 PKG_BUILD_PARALLEL:=1
@@ -57,6 +57,7 @@ MAKE_FLAGS = \
 	NO_LIBUNWIND=1 \
 	NO_LIBZSTD=1 \
 	NO_LIBCAP=1 \
+	NO_SHELLCHECK=1 \
 	BUILD_BPF_SKEL=0 \
 	CROSS_COMPILE="$(TARGET_CROSS)" \
 	CC="$(TARGET_CC)" \