Perform the silentoldconfig step of seabios before full make

I was running into a race condition when rebuilding seabios with a high cpu count,
resulting in failure with this error message:

cc1: fatal error: can't open 'out/src/asm-offsets.s' for writing: No such file or directory

Performing the silentoldconfig step before the full make step seems to resolve the failure.

resources/scripts/build/payload/seabios

@@ -40,6 +40,7 @@ cd seabios/
 # for libgfxinit setup:
 [[ -f Makefile ]] && make distclean
 cp ../resources/seabios/config/libgfxinit .config
+make silentoldconfig -j$(nproc)
 make -j$(nproc)
 mv out/bios.bin.elf ../payload/seabios/seabios_libgfxinit.elf
 mv out/vgabios.bin ../payload/seabios/seavgabios.bin
@@ -48,6 +49,7 @@ rm .config
 # for vgarom setup:
 [[ -f Makefile ]] && make distclean
 cp ../resources/seabios/config/vgarom .config
+make silentoldconfig -j$(nproc)
 make -j$(nproc)
 mv out/bios.bin.elf ../payload/seabios/seabios_vgarom.elf
 rm .config