src upgrade locally vs nfs from RELENG_12 to RELENG_13

Hi All,

Starting to plan to upgrade a few remaining RELENG_12 servers to 13.  
Was hoping I could just do an nfs mount of /usr/src and /usr/obj of a 13 
build server, but it does not seem to work when going from RELENG_12 to 
RELENG_13.

root@proxytest:/usr/src # make installkernel
--------------------------------------------------------------
 >>> Install check kernel
--------------------------------------------------------------
--------------------------------------------------------------
 >>> Installing kernel GENERIC on Mon Feb 12 20:58:06 UTC 2024
--------------------------------------------------------------
cd /usr/obj/usr/src/amd64.amd64/sys/GENERIC;  MACHINE_ARCH=amd64 
MACHINE=amd64  CPUTYPE= CC="cc -target x86_64-unknown-freebsd13.3 
--sysroot=/usr/obj/usr/src/amd64.amd64/tmp 
-B/usr/obj/usr/src/amd64.amd64/tmp/usr/bin" CXX="c++  -target 
x86_64-unknown-freebsd13.3 --sysroot=/usr/obj/usr/src/amd64.amd64/tmp 
-B/usr/obj/usr/src/amd64.amd64/tmp/usr/bin"  CPP="cpp -target 
x86_64-unknown-freebsd13.3 --sysroot=/usr/obj/usr/src/amd64.amd64/tmp 
-B/usr/obj/usr/src/amd64.amd64/tmp/usr/bin"  AS="as" AR="ar" 
ELFCTL="elfctl" LD="ld"  LLVM_LINK="" NM=nm OBJCOPY="objcopy" 
RANLIB=ranlib STRINGS=  SIZE="size" STRIPBIN="strip" 
PATH=/usr/obj/usr/src/amd64.amd64/tmp/bin:/usr/obj/usr/src/amd64.amd64/tmp/usr/sbin:/usr/obj/usr/src/amd64.amd64/tmp/usr/bin:/usr/obj/usr/src/amd64.amd64/tmp/legacy/usr/sbin:/usr/obj/usr/src/amd64.amd64/tmp/legacy/usr/bin:/usr/obj/usr/src/amd64.amd64/tmp/legacy/bin:/usr/obj/usr/src/amd64.amd64/tmp/legacy/usr/libexec::/sbin:/bin:/usr/sbin:/usr/bin 
make  KERNEL=kernel install
ld-elf.so.1: /usr/obj/usr/src/amd64.amd64/tmp/legacy/usr/sbin/make: 
Undefined symbol "regcomp@FBSD_1.6"
*** Error code 1

Stop.
make[1]: stopped in /usr/src
*** Error code 1

root@proxytest:/usr/src #


But if I clone the releng13 source locally and then do a make 
buildworld/buildkernel, doing a make installkernel works.  Is there a 
way to get it to work over nfs ? What do I need to build on the 
buildserver so I dont have to build locally each time on the RELENG_12 
boxes I want to upgrade ?

     ---Mike