Fix depfile parser handling of multiple rules
Currently we handle Makefile rules of the form:
out: in1 in2 in3
and the form:
out: in1 \
in2 \
in3
Teach the depfile parser to handle the additional form:
out: in1
out: in2
out: in3
This is also valid Makefile syntax and is the depfile format
generated by the Intel Compiler for Windows.
Note that the `gcc -MP` option adds empty phony rules to the generated
Makefile fragment:
out: in1 in2 in3
in1:
in2:
in3:
Previously we tolerated these because they were treated as inputs, which
was accidentally correct. Instead we must now tolerate these by
ignoring targets for which no dependencies are specified.
3 files changed
