[gtk/gtk-3-24] build/win32/config-msvc.mak.in: Define a default PREFIX

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

commit 80c14d7cf999c512635b89c9ed1f4c59fb063ba9
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Wed Jul 31 15:47:01 2019 +0800

    build/win32/config-msvc.mak.in: Define a default PREFIX
    
    If PREFIX was not passed when invoking generate-msvc.mak, define a
    default PREFIX that is consistent with the MSVC project files, for
    convenience.

 build/win32/config-msvc.mak.in | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/build/win32/config-msvc.mak.in b/build/win32/config-msvc.mak.in
index c1d0b62f1d..69cf931b60 100644
--- a/build/win32/config-msvc.mak.in
+++ b/build/win32/config-msvc.mak.in
@@ -2,6 +2,11 @@
 
 !include detectenv-msvc.mak
 
+# Default prefix if not defined
+!ifndef PREFIX
+PREFIX=..\..\vs$(VSVER)\$(PLAT)
+!endif
+
 # Configurable paths to the various interpreters we need
 !ifndef PERL
 PERL = perl