Stop messing with LDFLAGS when cross-compiling

LDFLAGS cannot be used to link to specific versions, instead
we should use extconf '--with-opt-dir'.
Return recipe definition for SQLite3

Return the recipe so it can be used to adjust other cross-compilation
options of sqlite3 extension.
Use extconf's '--with-opt-dir' to proper link

On Linux, LDFLAGS cannot be used during cross-compilation and was
resulting in problems.

We use --with-opt-dir to point the right headers/libs location for
that platform.
Retrieve cross-compile host from CC (not host)

Use this to build sqlite3 for the right platform since the generated
triplet for i586-mingw32msvc was incorrect.

Feed the recipe installation location to the cross-configure options
so the Ruby extension finds the proper headers and libs.
Build all the cross ports when 'cross' is invoked

Since 'x64-mingw32' might not get defined on Ruby 1.8.7, we use
this so all the ports get compiled before usage.