Start work on caching coastline

HelenOS headers and libraries are copied to the build directory, thus
allowing to rebuild HelenOS for other architectures. The big advantage
is that after first coastline build you do not need to care whether
HelenOS is configured for the rigth architecture.

This is a first commit from the transition to caching scheme, some
packages may no longer work. Will be fixed later.
Prevent installation into non-matching architecture
gcc: update to use the cache
Remove invalid action
Check for errors when initializing the cache
Add init for build directory initialization
Fix initialization of arch in config file
Populate the cache after initialization
Remove extra equal sign
hsct.sh init ... build forces rebuild

Otherwise, partially built system could be treated as a fully built one.
Add softfloat where needed
Headers in libc are not on include path

Thus, all includes in libc headers must use the libc/ directory
specification.
Support for other architectures
Add softfloat for some architectures
Copy libclui to cache (MSIM dependency)
msim: update to use cache
update command for cache refreshing
Remember the configuration
Allow forced rebuild when updating
Store machine name as well