Allow disabling of -fPIC for libraries.

Change-Id: I9abb13a057530d16013ad889cea2acc34576c467
Reviewed-by: Jake Petroules <jake.petroules@petroules.com>
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
Add support for compiling assembler files with GCC.

Task-number: QBS-437
Change-Id: I7d4b64df16f5a260d41a6d34335fe0cc1a36b712
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>