configure: don't enable firmware for targets that are not built

This avoids the unfortunate effect of building pc-bios blobs
even for targets the user isn't interested in.

Due to the bi-arch nature of x86 and PPC firmware, check for the
desired target by hand, and don't just look for the compilation target
in $target_list.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

configure

@@ -1841,6 +1841,16 @@ compute_target_variable() {
   fi
 }
 
+have_target() {
+  for i; do
+    case " $target_list " in
+      *" $i "*) return 0;;
+      *) ;;
+    esac
+  done
+  return 1
+}
+
 # probe_target_compiler TARGET
 #
 # Look for a compiler for the given target, either native or cross.
@@ -2261,8 +2271,9 @@ echo "# Automatically generated by configure - do not modify" > Makefile.prereqs
 
 # Mac OS X ships with a broken assembler
 roms=
-if test "$targetos" != "darwin" && test "$targetos" != "sunos" && \
-        test "$targetos" != "haiku" && test "$softmmu" = yes && \
+if have_target i386-softmmu x86_64-softmmu && \
+        test "$targetos" != "darwin" && test "$targetos" != "sunos" && \
+        test "$targetos" != "haiku" && \
         probe_target_compiler i386-softmmu; then
     roms="pc-bios/optionrom"
     config_mak=pc-bios/optionrom/config.mak
@@ -2271,7 +2282,8 @@ if test "$targetos" != "darwin" && test "$targetos" != "sunos" && \
     write_target_makefile >> $config_mak
 fi
 
-if test "$softmmu" = yes && probe_target_compiler ppc-softmmu; then
+if have_target ppc-softmmu ppc64-softmmu && \
+        probe_target_compiler ppc-softmmu; then
     roms="$roms pc-bios/vof"
     config_mak=pc-bios/vof/config.mak
     echo "# Automatically generated by configure - do not modify" > $config_mak
@@ -2281,7 +2293,7 @@ fi
 
 # Only build s390-ccw bios if the compiler has -march=z900 or -march=z10
 # (which is the lowest architecture level that Clang supports)
-if test "$softmmu" = yes && probe_target_compiler s390x-softmmu; then
+if have_target s390x-softmmu && probe_target_compiler s390x-softmmu; then
   write_c_skeleton
   do_compiler "$target_cc" $target_cc_cflags -march=z900 -o $TMPO -c $TMPC
   has_z900=$?