[gobject-introspection] MSVC builds: Fix previous commit

[Chun-wei Fan <fanchunwei src gnome org>]

commit b25f9436e0e2f3cec88d87eae94f2d55eab0cfcc
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Fri Mar 11 16:40:00 2016 +0800

    MSVC builds: Fix previous commit
    
    We need to get the full, complete path for $(PREFIX) for all cases, not
    just when using the default prefix.

 build/win32/introspection-msvc.mak |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/build/win32/introspection-msvc.mak b/build/win32/introspection-msvc.mak
index fe4fa67..6b58293 100644
--- a/build/win32/introspection-msvc.mak
+++ b/build/win32/introspection-msvc.mak
@@ -9,12 +9,13 @@
 
 !if "$(PREFIX)" == ""
 PREFIX = ..\..\..\vs$(VSVER)\$(PLAT)
-!if ![setlocal]        && \
-    ![set PFX=$(PREFIX)] && \
+!endif
+
+!if ![setlocal]                && \
+    ![set PFX=$(PREFIX)]       && \
     ![for %P in (%PFX%) do @echo PREFIX_FULL=%~dpnfP > pfx.x]
 !endif
 !include pfx.x
-!endif
 
 !if "$(PKG_CONFIG_PATH)" == ""
 PKG_CONFIG_PATH=$(PREFIX_FULL)\lib\pkgconfig