configure: Add quotes around a variable which might be empty

If we only have a target compiler but no host compiler, the $type
variable will be empty once.

(Currently we fail to do a cross build if no host compiler is available
due to using the host compiler for processing option lists though.
But despite that, this comparison in configure needs quotes.)

Signed-off-by: Martin Storsjö <martin@martin.st>

configure

@@ -5033,7 +5033,7 @@ fi
 for pfx in "" host_; do
     varname=${pfx%_}cc_type
     eval "type=\$$varname"
-    if [ $type = "msvc" ]; then
+    if [ "$type" = "msvc" ]; then
         check_${pfx}cc <<EOF || add_${pfx}cflags -Dinline=__inline
 static inline int foo(int a) { return a; }
 EOF