Configuration goes wrong when LOCAL_SRCS contains generated files

[buzden]

ARDUINO_LIBS variable is calculated during configuration and it uses LOCAL_SRCS variable for this: https://github.com/sudar/Arduino-Makefile/blob/6f786a96b0acfb0c9b2d2f4e39911d2803088729/Arduino.mk#L974

But when LOCAL_SRCS contains files that are to be generated by some target in the user's makefile, we get sed piss off during configuration:

...
- [MANUAL]             NO_CORE_MAIN_CPP set so core library will not include main.cpp
- [ASSUMED]            MONITOR_BAUDRATE = 9600 
sed: can't read Blink.c: No such file or directory
sed: can't read Blink.c: No such file or directory
sed: can't read Blink.c: No such file or directory
sed: can't read Blink.c: No such file or directory
sed: can't read Blink.c: No such file or directory
sed: can't read Blink.c: No such file or directory
sed: can't read Blink.c: No such file or directory
sed: can't read Blink.c: No such file or directory
sed: can't read Blink.c: No such file or directory
sed: can't read Blink.c: No such file or directory
sed: can't read Blink.c: No such file or directory
sed: can't read Blink.c: No such file or directory
sed: can't read Blink.c: No such file or directory
sed: can't read Blink.c: No such file or directory
sed: can't read Blink.c: No such file or directory
sed: can't read Blink.c: No such file or directory
- [DEFAULT]            OPTIMIZATION_LEVEL = s 
...

Blink.c here is those C-file that was added manually to LOCAL_C_SRCS and is generated by user-defined target.