Add hack to flx re flx_pkgconfig. Undo previous hack.

Use ---framework=Carbon in flx_pkgconfig database *.fpc
files. flx translates this to two arguments -framework Carbon.
This crud is required so a unique list of linker arguments
can be formed: flx_pkgconfig requires a single string for all
arguments but the linker requires two separate arguments
on the command line.

Note this is done by flx_pkg, NOT flx_pkgconfig.
Undid the previous hackery which passed --keepall to fix this,
revert back to --keepleftmost.

Also add -od flag to flx, specifies (existant) directory
to put final product file (executable).