[metacity] build: fix builddir != srcdir

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 6389b08b4f491947c3745441cd3034a6689472f6
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Sat Feb 29 12:42:41 2020 +0200

    build: fix builddir != srcdir

 src/Makefile.am | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/src/Makefile.am b/src/Makefile.am
index 373c653c..97104dd0 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -16,6 +16,7 @@ AM_CPPFLAGS = \
        -DSN_API_NOT_YET_FROZEN=1 \
        -I$(srcdir)/core \
        -I$(srcdir)/include \
+       -I$(builddir)/core \
        -I$(top_srcdir) \
        $(NULL)
 
@@ -196,7 +197,7 @@ testasyncgetprop_CFLAGS = \
        $(NULL)
 
 ENUM_TYPES = \
-       core/window-private.h \
+       $(srcdir)/core/window-private.h \
        $(NULL)
 
 core/meta-enum-types.c: core/meta-enum-types.c.in core/meta-enum-types.h $(ENUM_TYPES)