dependencies/pkgconfig: Fix found state ignoring errors

Previously even when meson failed to obtain cflags or libs for a
dependency it would lead to the dependency being found, causing very
confusing errors at build time.

mesonbuild/dependencies/base.py

@@ -649,6 +649,8 @@ class PkgConfigDependency(ExternalDependency):
         if ret != 0:
             return
 
+        self.is_found = True
+
         try:
             # Fetch cargs to be used while using this dependency
             self._set_cargs()
@@ -663,8 +665,6 @@ class PkgConfigDependency(ExternalDependency):
                 self.is_found = False
                 self.reason = e
 
-        self.is_found = True
-
     def __repr__(self):
         s = '<{0} {1}: {2} {3}>'
         return s.format(self.__class__.__name__, self.name, self.is_found,