coreinfo: Make better calls to libpayload build scripts

Set LPGCC and LPAS so that CC and AS are maintained.
Clean up the makefile order to check for .config to be easier to
read.
Use objcopy instead of strip and keep the debug symbols file.

Change-Id: I95d6b7a0e3a99a142d3fd6e2ecc61de1d4412402
Signed-off-by: Marc Jones <marc.jones@se-eng.com>
Reviewed-on: http://review.coreboot.org/1994
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
1 file changed