builds fail with GNU make v. 3.82

[dagit]

Converted from SourceForge issue 3413309, submitted by jean_utke

For changeset b7386ff

the make invocation fails with:
cd /sandbox/Argonne/git/fortran-parser/src/fortran/ofp; make
make[1]: Entering directory /sandbox/Argonne/git/fortran-parser/src/fortran/ofp' cd parser ; make make[2]: Entering directory/sandbox/Argonne/git/fortran-parser/src/fortran/ofp/parser'
cd java ; make
make[3]: Entering directory `/sandbox/Argonne/git/fortran-parser/src/fortran/ofp/parser/java'
Makefile:161: *** mixed implicit and normal rules. Stop.

The problem comes from the evaluation of the make variables in this Makefile in the following sequence:
....
DATE=date "+20%y%m%d"
...
ALT_JARFILE=OpenFortranParser-$(DATE).jar
....and line 161:
$(BUILDDIR)/$(ALT_JARFILE): $(CLASS_FILES)

and here DATE isn't evaluated (yet) when the error is reported. Instead I assume the "%" in tbe string is interpreted as a suffix start.
Hence the error message.
Resetting "DATE" to some other string constant makes the problem disappear.