Makefile: Fix git rev fallback path for non-git checkouts

[AndrewPiroli]

Looks like an extra quote got left behind when refactoring this in b0e74f0 Before:

make[1]: Entering directory '/home/apiroli/work/priiloader-me/priiloader'

!!!!!!WARNING!!!!!!!
--------------------
NOT BUILDING FROM GIT CHECKOUT. REV NUMBERS WILL NOT MAKE ANY SENSE

/bin/sh: 1: Syntax error: Unterminated quoted string
make[1]: *** [Makefile:162: pre_build] Error 2

After:

make[1]: Entering directory '/home/apiroli/work/priiloader-me/priiloader'

!!!!!!WARNING!!!!!!!
--------------------
NOT BUILDING FROM GIT CHECKOUT. REV NUMBERS WILL NOT MAKE ANY SENSE

Using 0x21477 as revision, 21477-no-git as revision string

-----------------------------------------------
compiling priiloader...

Fixes: #321

[DacoTaco]

ah ye, i saw it this morning and wanted to look into it after work haha thanks andy!