Detecting FreeBSD's make

[Harlan Stenn]

I'm getting bitten by the VPATH-handling differences between FreeBSD's
make and gmake.

I have a .y file and I currently distribute the bison-generated .[ch]
files in the distribution.

On a stock FreeBSD machine (at least) when doing a build outside of the
source tree, FreeBSD's make doesn't see the corresponding .y->.[ch]
files from its vantage point in the builddir, so it fires up byacc to
generate the files.

The byacc-generated parser code is different from what bison produced,
and we get a "syntax error" parsing the target file.  Yes, we want to
find and fix this discrepancy.  We also want to improve the parsing
error messages.

And as a work-around (at least), if I can detect that the build
environment is using a 'make' that has this VPATH difference, I can go
ahead and copy/link the generated .[ch] files from the srcdir into the
builddir and also "solve" the problem that way.

Thoughts/suggestions?

H