Fix deptypes for deps specified on command line (#2307)

Fixes #2306

Any dependency explicitly mentioned in a spec string ended up with the
build and link deptypes unconditionally. This fixes dependency
resolution to ensure that packages which are mentioned in the spec
string have their deptypes determined by the dependency information
in the package.py files. For example if a package has cmake as a build
dependency, and cmake is mentioned as a dependency in the spec string
for the package, then it ends up with just the build deptype.