configure: do not limit Hypervisor.framework test to Darwin

Because the target/i386/hvf/meson.build rule culls hvf support
on non-Darwin systems, a --enable-hvf build is succeeding.
To fix this, just try the compilation test every time someone
passes --enable-hvf.

Reported-by: Christophe de Dinechin <dinechin@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

configure

@@ -870,7 +870,7 @@ Darwin)
   bsd="yes"
   darwin="yes"
   hax="yes"
-  hvf="yes"
+  hvf=""
   if [ "$cpu" = "x86_64" ] ; then
     QEMU_CFLAGS="-arch x86_64 $QEMU_CFLAGS"
     QEMU_LDFLAGS="-arch x86_64 $QEMU_LDFLAGS"
@@ -5823,16 +5823,18 @@ fi
 
 #################################################
 # Check to see if we have the Hypervisor framework
-if [ "$darwin" = "yes" ] ; then
+if [ "$hvf" != "no" ] ; then
   cat > $TMPC << EOF
 #include <Hypervisor/hv.h>
 int main() { return 0;}
 EOF
   if ! compile_object ""; then
+    if test "$hvf" = "yes"; then
+	error_exit "Hypervisor.framework not available"
+    fi
     hvf='no'
   else
     hvf='yes'
-    QEMU_LDFLAGS="-framework Hypervisor $QEMU_LDFLAGS"
   fi
 fi