[openwrt/openwrt] kernel-build.mk: Fix multi-core build warning.

[LEDE Commits]

robimarko pushed a commit to openwrt/openwrt.git, branch main:
https://git.openwrt.org/7ada5ab1c98a4b8902000e28c1ffa5ca2e6959c4

commit 7ada5ab1c98a4b8902000e28c1ffa5ca2e6959c4
Author: Zxl hhyccc <zxlhhy at gmail.com>
AuthorDate: Fri Oct 4 22:31:25 2024 +0800

    kernel-build.mk: Fix multi-core build warning.
    
    In the case of multi-core compilation, the warning prompts to add a "+" sign.
    ````
    warning: jobserver unavailable: using -j1. Add `+' to parent make rule.
    `````
    Signed-off-by: Zxl hhyccc <zxlhhy at gmail.com>
    Link: https://github.com/openwrt/openwrt/pull/16598
    Signed-off-by: Robert Marko <robimarko at gmail.com>
---
 include/kernel-build.mk | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/kernel-build.mk b/include/kernel-build.mk
index 48e00fa4c6..404c318d41 100644
--- a/include/kernel-build.mk
+++ b/include/kernel-build.mk
@@ -154,7 +154,7 @@ define BuildKernel
   download: $(if $(LINUX_SITE),$(DL_DIR)/$(LINUX_SOURCE))
   prepare: $(STAMP_PREPARED)
   compile: $(LINUX_DIR)/.modules
-	$(MAKE) -C image compile TARGET_BUILD=
+	+$(MAKE) -C image compile TARGET_BUILD=
 
   dtb: $(STAMP_CONFIGURED)
 	$(_SINGLE)$(KERNEL_MAKE) scripts_dtc