Just sharing something I learned in case it helps others who have
an interest in a "mixed compiler" pkgsrc build environment. That
is, buiding packages with gcc that might depend on packages built
with a native compiler (or vice versa).

This table simply shows the sequence of package builds leading
up to building tiff on Solaris (on x86 hardware). In the Yes/No
column, Yes just means it worked, No means it didn't.

The abbreviation "SS 10" refers to the latest Sun compiler tools,
Sun Studio 10 (not to be confused with Solaris 10).

1.  libtool-base, build with SS 10: Yes
2.  jpeg, build with SS 10:         Yes
3a. tiff, build with SS 10:         No
3b. tiff, build with gcc:           No

1.  libtool-base, build with gcc:   Yes
2.  jpeg, build with gcc:           Yes
3a. tiff, build with gcc:           Yes
3b. tiff, build with SS 10:         (not tried)

My take away from this: If you're using other compilers in
combination w/ gcc libtool-base must be built with gcc.