I was able to build from Git and flash using flashrom.
flashrom --verbose --programmer internal:laptop=force_I_want_a_brick --chip SST25VF016B --read macbook21_usqwerty_vesafb.rom >flashrom_read.log 2>&1
This worked fine for me. Erase/write done. Verifying flash... VERIFIED. Restoring MMIO space at 0xb7645070 Restoring MMIO space at 0xb764507c Restoring MMIO space at 0xb7645078 Restoring MMIO space at 0xb7645076 Restoring MMIO space at 0xb7645074 Restoring PCI config space for 00:1f:0 reg 0xdc
