gcc-package-target: don't fail if the .la files we try to delete are not there to start with
This fixes:
| rm: cannot remove `/OE/tentacle/build/tmp-angstrom_2010_x-eglibc/work/armv7a-angstrom-linux-gnueabi/gcc-4.5-r39.1+svnr175127/image/usr/libexec/gcc/arm-angstrom-linux-gnueabi/4.5.4/*.la': No such file or directory
| ERROR: Function 'do_install' failed (see /OE/tentacle/build/tmp-angstrom_2010_x-eglibc/work/armv7a-angstrom-linux-gnueabi/gcc-4.5-r39.1+svnr175127/temp/log.do_install.19514 for further information)
NOTE: package gcc-4.5-r39.1+svnr175127: task do_install: Failed
