objtool wrapper: use absolute path to call the wrapper

Older kernel versions run make outside of the build directory. This
works since all paths are absolute. Relative paths will fail in such
a scenario.

Use an absolute path to the objtool wrapper as well, since the
relative path breaks the build on older kernels.

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Attila Fülöp <[email protected]>
Closes #17541

Author: AttilaFueloep

module/Makefile.in

@@ -57,7 +57,7 @@ modules-Linux:
 		$(if @KERNEL_LD@,LD=@KERNEL_LD@) $(if @KERNEL_LLVM@,LLVM=@KERNEL_LLVM@) \
 		$(if @KERNEL_CROSS_COMPILE@,CROSS_COMPILE=@KERNEL_CROSS_COMPILE@) \
 		$(if @KERNEL_ARCH@,ARCH=@KERNEL_ARCH@) \
-		$(if @OBJTOOL_DISABLE_WERROR@,objtool=@top_builddir@/scripts/objtool-wrapper) \
+		$(if @OBJTOOL_DISABLE_WERROR@,objtool=@abs_top_builddir@/scripts/objtool-wrapper) \
 		M="$$PWD" @KERNEL_MAKE@ CONFIG_ZFS=m modules
 
 modules-FreeBSD: