[yocto] Strange error trying to use externalsrc

[Matt Schuckmann]

I'm trying to use the externalsrc class to make it easier build an application under active development. 

I'm working off of the Dylan branch. 

If I add the following 2 lines to my site.conf

INHERIT += "externalsrc"
S_pn-keypadd = "/home/dev/builds/zanzibar/keypadd"

I get the following error when I try to build the keypadd recipe. 

ERROR: Function failed: gnu-config-native: LIC_FILES_CHKSUM points to an invalid file: /home/dev/builds/zanzibar/tisdk/zanzibar/build/arago-tmp-external-linaro-toolchain/work/i686-linux/gnu-config-native/20120814-r0/gnu-config-20120814/config.guess
ERROR: Logfile of failure stored in: /home/dev/builds/zanzibar/tisdk/zanzibar/build/arago-tmp-external-linaro-toolchain/work/i686-linux/gnu-config-native/20120814-r0/temp/log.do_configure.11698
Log data follows:
| DEBUG: Executing python function sysroot_cleansstate
| DEBUG: Python function sysroot_cleansstate finished
| DEBUG: Executing shell function do_configure
| DEBUG: Shell function do_configure finished
| DEBUG: Executing python function do_qa_configure
| NOTE: Checking autotools environment for common misconfiguration
| DEBUG: Python function do_qa_configure finished
| ERROR: Function failed: gnu-config-native: LIC_FILES_CHKSUM points to an invalid file: /home/dev/builds/zanzibar/tisdk/zanzibar/build/arago-tmp-external-linaro-toolchain/work/i686-linux/gnu-config-native/20120814-r0/gnu-config-20120814/config.guess
ERROR: Task 26 (virtual:native:/home/dev/builds/zanzibar/tisdk/zanzibar/sources/oe-core/meta/recipes-devtools/gnu-config/gnu-config_20120814.bb, do_configure) failed with exit code '1'


The keypadd recipe is marked as CLOSED but I've also tried MIT and GPL. I've even added a license file and MD5 checksum. 
Interestingly externalsrc seems to work if I add these 2 lines to the recipe. 

inherit externalsrc
S = "/home/dev/builds/zanzibar/keypadd"

But I don't want to have to edit the recipe every time I want to switch to building from a local directory. 

Any suggestions as to what is wrong? 

Thanks,
Matt S.