Make boost dependency symmetric with the rest.

[brettviren]

Out of laziness, the waf tool boost was used copied into waf-tools/ in order to build against Boost. It is full featured but works differently from the rest. In particular, if one has a prefix with all dependencies one can not do:

$ ./wcb configure --prefix=$PREFIX

But, instead one must specifically notify the boost tool with:

$ ./wcb configure --prefix=$PREFIX \
     --boost-mt --boost-libs=$PREFIX/lib \
     --boost-include=$PREFIX/include

When boost is not correctly directed will pick up the system install and the only indication is if the user notices a version match. Eg on Debian 12 we see

Checking boost includes                     : 1.74.0

instead of the desired Spack version:

Checking boost includes                     : 1.85.0

Probably the best solution it to hack boost.py tool to:

• use "standard" --with-* type flags
• make --boost-mt set by default
• honor --prefix value as a potential location