Make BTF generation reproducible

https://bugzilla.opensuse.org/show_bug.cgi?id=1230414

Index: linux-6.10/scripts/Makefile.btf
===================================================================
--- linux-6.10.orig/scripts/Makefile.btf
+++ linux-6.10/scripts/Makefile.btf
@@ -12,7 +12,7 @@ endif
 
 pahole-flags-$(call test-ge, $(pahole-ver), 121)	+= --btf_gen_floats
 
-pahole-flags-$(call test-ge, $(pahole-ver), 122)	+= -j
+pahole-flags-$(call test-ge, $(pahole-ver), 122)	+= -j1
 
 ifeq ($(pahole-ver), 125)
 pahole-flags-y	+= --skip_encoding_btf_inconsistent_proto --btf_gen_optimized
@@ -21,7 +21,7 @@ endif
 else
 
 # Switch to using --btf_features for v1.26 and later.
-pahole-flags-$(call test-ge, $(pahole-ver), 126)  = -j --btf_features=encode_force,var,float,enum64,decl_tag,type_tag,optimized_func,consistent_func
+pahole-flags-$(call test-ge, $(pahole-ver), 126)  = -j1 --btf_features=encode_force,var,float,enum64,decl_tag,type_tag,optimized_func,consistent_func
 
 endif