jom: dependency automatic variable $? does behave different on non-existing targets

jom 1.0.14 does not handle $? correctly

Makefile

out.txt: Makefile
	@echo "$?"
	@echo "$**"
	@echo "$@"

Case 1: out.txt newer than Makefile

jom and nmake do not touch the build rules. Cool.

Case 2: out.txt older than Makefile

Same behavior, cool.

nmake (msvc2013) output:

"Makefile"
"Makefile"
"out.txt"

jom 1.0.14 output:

"Makefile"
"Makefile"
"out.txt"

Case 3: out.txt does not exist

Here is where the touble begins

nmake (msvc2013) output:

"Makefile"
"Makefile"
"out.txt"

jom 1.0.14 output:

""
"Makefile"
"out.txt"

Both commands run from the Developer Command Line Prompt for VS2013