CPPFLAGS, CFLAGS, CXXFLAGS and LDFLAGS are supposed to be under
user-control and putting configure-determined options in them broke
something as simple as running "make CXXFLAGS=-Wno-some-extra-warning"
because this overrode the CXXFLAGS set by configure and required for
build.
Improve this by using WX_*FLAGS in the generated makefile and leaving
the user-controlled FLAGS alone. This is still not ideal as running
"configure CFLAGS=-DFOO" and then "make CFLAGS=-DBAR" will define both
FOO and BAR, as configure copies CFLAGS to WX_CFLAGS, and so setting it
on make command line won't override it, as it should, but this should be
a much more rare and also much less severe problem, so we should be able
to live with it for now.
Normally this commit shouldn't result in any user-visible changes, i.e.
it shouldn't break any previously working scenarios and only make some
previously broken ones work.
ec091c9f2b
