OvmfPkg/build.sh: Make GCC5 the default toolchain, catch GCC43 and earlier

OvmfPkg/build.sh: Make GCC5 the default toolchain, catch GCC43 and earlier

v2:
 * Changes suggested by Laszlo:
   - change the catch-all (*) to GCC5, from GCC44
   - remove the (5.*.*) pattern from GCC49
   - generate error for GCC < 4.4

In v3, also generate error for really GCC < 4.4, like GCC 1.

Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Bugzilla: https://bugzilla.tianocore.org/show_bug.cgi?id=62
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Konrad Rzeszutek Wilk <konrad@kernel.org>
Tested-by: Laszlo Ersek <lersek@redhat.com>