do a "defconfig + elconfig" to get a .config

- Copy rhel/diff.config to config-aarch64.
- Enable building the kernel config in such a way that the defconfig's
  options are _used_ but certain RHEL-specific options are overridden.
- The build salt got carried over from the RHEL diff.config, remove that.
- Unset CONFIG_DEBUG_INFO_REDUCED so that CONFIG_DEBUG_INFO_BTF can be
  enabled. Otherwise the build fails at the step where the bpftool
  package gets built.

kernel-common.inc

@@ -128,7 +128,8 @@
 %define bldarch x86_64
 %define hdrarch x86_64
 %define make_target bzImage
-%define kernel_image arch/x86/boot/bzImage
+%define kernel_image arch/%{asmarch}/boot/%{make_target}
+%define defconfig arch/%{asmarch}/configs/%{bldarch}_defconfig
 %endif
 
 %ifarch aarch64
@@ -136,9 +137,12 @@
 %define bldarch arm64
 %define hdrarch arm64
 %define make_target Image.gz
-%define kernel_image arch/arm64/boot/Image.gz
+%define kernel_image arch/%{asmarch}/boot/%{make_target}
+%define defconfig arch/%{asmarch}/configs/defconfig
 %endif
 
+%define elconfig arch/%{asmarch}/configs/el.config
+
 %if %{with_vdso_install}
 %define use_vdso 1
 %define _use_vdso 1
@@ -555,19 +559,19 @@ pathfix.py -i "%{__python3} %{py3_shbang_opts}" -n -p \
 
 mv COPYING COPYING-%{version}-%{release}
 
-cp -a %{SOURCE2} .
-cp -a %{SOURCE4} .
+cp %{_sourcedir}/config-$(uname -m) %{elconfig}
 
 # Set the EXTRAVERSION string in the top level Makefile.
 sed -i "s@^EXTRAVERSION.*@EXTRAVERSION = -%{release}.%{_target_cpu}@" Makefile
 
 %ifarch x86_64 || aarch64
-cp config-%{_target_cpu} .config
+./scripts/kconfig/merge_config.sh %{defconfig} %{elconfig}
 %{__make} ARCH=%{bldarch} listnewconfig | grep -E '^CONFIG_' > newoptions-el9-%{_target_cpu}.txt || true
 if [ -s newoptions-el9-%{_target_cpu}.txt ]; then
 	cat newoptions-el9-%{_target_cpu}.txt
 fi
 rm -f newoptions-el9-%{_target_cpu}.txt
+rm -vf .config*
 %endif
 
 # Add DUP and kpatch certificates to system trusted keys for RHEL.
@@ -575,17 +579,17 @@ rm -f newoptions-el9-%{_target_cpu}.txt
 openssl x509 -inform der -in %{SOURCE100} -out rheldup3.pem
 openssl x509 -inform der -in %{SOURCE101} -out rhelkpatch1.pem
 cat rheldup3.pem rhelkpatch1.pem > certs/rhel.pem
-for i in config-*; do
+for i in %{elconfig}; do
 	sed -i 's@CONFIG_SYSTEM_TRUSTED_KEYS="*"@CONFIG_SYSTEM_TRUSTED_KEYS="certs/rhel.pem"@' $i
 done
 %else
-for i in config-*; do
+for i in %{elconfig}; do
         sed -i 's@CONFIG_SYSTEM_TRUSTED_KEYS="*"@CONFIG_SYSTEM_TRUSTED_KEYS=""@' $i
 done
 %endif
 
 # Adjust the FIPS module name for RHEL9.
-for i in config-*; do
+for i in %{elconfig}; do
 	sed -i 's@CONFIG_CRYPTO_FIPS_NAME=.*@CONFIG_CRYPTO_FIPS_NAME="Red Hat Enterprise Linux 9 - Kernel Cryptographic API"@' $i
 done
 
@@ -597,9 +601,7 @@ popd > /dev/null
 pushd linux-%{KVERREL} > /dev/null
 
 %ifarch x86_64 || aarch64
-cp config-%{_target_cpu} .config
-
-%{__make} ARCH=%{bldarch} oldconfig
+./scripts/kconfig/merge_config.sh %{defconfig} %{elconfig}
 
 %if %{signkernel} || %{signmodules}
 cp %{SOURCE23} certs/