[source] x86: stop relying on hexdump for image build signature

[LEDE Commits]

nbd pushed a commit to source.git, branch master:
https://git.lede-project.org/?p=source.git;a=commitdiff;h=d5ee23ee275fcd6550b0051de59706cc928cdac8

commit d5ee23ee275fcd6550b0051de59706cc928cdac8
Author: Felix Fietkau <nbd at nbd.name>
AuthorDate: Sun Jul 3 18:39:08 2016 +0200

    x86: stop relying on hexdump for image build signature
    
    Use perl to generate random number instead.
    See https://github.com/freifunk-gluon/gluon/issues/811
    
    Signed-off-by: Felix Fietkau <nbd at nbd.name>
---
 target/linux/x86/image/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/linux/x86/image/Makefile b/target/linux/x86/image/Makefile
index d33d1b4..93b7fca 100644
--- a/target/linux/x86/image/Makefile
+++ b/target/linux/x86/image/Makefile
@@ -40,7 +40,7 @@ ifneq ($(GRUB_TERMINALS),)
   GRUB_TERMINAL_CONFIG := terminal_input $(GRUB_TERMINALS); terminal_output $(GRUB_TERMINALS)
 endif
 
-SIGNATURE:=$(shell dd if=/dev/urandom bs=4 count=1 2>/dev/null | hexdump -v -e '"%08x"')
+SIGNATURE:=$(shell perl -e 'printf("%08x", rand(0xFFFFFFFF))')
 ROOTPART:=$(call qstrip,$(CONFIG_TARGET_ROOTFS_PARTNAME))
 ROOTPART:=$(if $(ROOTPART),$(ROOTPART),PARTUUID=$(SIGNATURE)-02)