[PATCH] kbuild: Fix compilation error

[Rong Tao]

From: Rong Tao <rongtao@xxxxxxxx>

In the absence of a CONFIG_FUNCTION_ALIGNMENT defined, -falign-functions=
will be given a null value, which results in a compilation error, as
follows:

    $ make -C samples/bpf/
    ...
    CC      /home/sdb/Git/linux/samples/bpf/syscall_nrs.s
    gcc: error: missing argument to ‘-falign-functions=’
    make[2]: *** [scripts/Makefile.build:118: /home/sdb/Git/linux/samples
        /bpf/syscall_nrs.s] Error 1
    make[1]: *** [Makefile:1996: /home/sdb/Git/linux/samples/bpf] Error 2
    make[1]: Leaving directory '/home/sdb/Git/linux'
    make: *** [Makefile:269: all] Error 2

Signed-off-by: Rong Tao <rongtao@xxxxxxxx>
---
 Makefile | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Makefile b/Makefile
index 6aa709df6bde..57cce4c8f8a2 100644
--- a/Makefile
+++ b/Makefile
@@ -1006,9 +1006,11 @@ KBUILD_CFLAGS	+= $(CC_FLAGS_CFI)
 export CC_FLAGS_CFI
 endif
 
+ifdef CONFIG_FUNCTION_ALIGNMENT
 ifneq ($(CONFIG_FUNCTION_ALIGNMENT),0)
 KBUILD_CFLAGS += -falign-functions=$(CONFIG_FUNCTION_ALIGNMENT)
 endif
+endif
 
 # arch Makefile may override CC so keep this after arch Makefile is included
 NOSTDINC_FLAGS += -nostdinc
-- 
2.38.1