configure: Check bzip2 is available

The bzip2 tool is not included in default installations.
On freshly installed systems, ./configure succeeds but 'make'
might fail later:

    BUNZIP2 pc-bios/edk2-i386-secure-code.fd.bz2
  /bin/sh: bzip2: command not found
  make: *** [Makefile:305: pc-bios/edk2-i386-secure-code.fd] Error 127
  make: *** Deleting file 'pc-bios/edk2-i386-secure-code.fd'
  make: *** Waiting for unfinished jobs....

Add a check in ./configure to warn the user if bzip2 is missing.

See also: 536d217 ("roms: build edk2 firmware binaries ...")
Reported-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20191108114531.21518-3-philmd@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Luc Michel <luc.michel@greensocs.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

configure

@@ -2154,6 +2154,10 @@ for target in $target_list; do
       ;;
   esac
 done
+# The EDK2 binaries are compressed with bzip2
+if test "$edk2_blobs" = "yes" && ! has bzip2; then
+  error_exit "The bzip2 program is required for building QEMU"
+fi
 
 feature_not_found() {
   feature=$1