[libgit2-glib] meson: Fix DESTDIR use in Windows

[Iñigo Martínez <inigomartinez src gnome org>]

commit 5e9bf6ddd96742209c546aa31dfdc9f6c7211266
Author: Iñigo Martínez <inigomartinez gmail com>
Date:   Mon Nov 12 13:29:40 2018 +0100

    meson: Fix DESTDIR use in Windows
    
    The use of DESTDIR in Windows produces some errors[0]. To fix this
    issue a different approach has been used for paths. Instead of using
    absolute paths, relative paths are used as meson does. One of this
    relative paths is used along with MESON_INSTALL_DESTDIR_PREFIX to
    avoid any issues.
    
    [0] https://github.com/Alexpux/MINGW-packages/pull/4560#issuecomment-431294899

 meson.build             | 7 +++----
 meson_python_compile.py | 4 +++-
 meson_vapi_link.py      | 7 ++-----
 3 files changed, 8 insertions(+), 10 deletions(-)
---
diff --git a/meson.build b/meson.build
index fddcb9c..3b4d2f4 100644
--- a/meson.build
+++ b/meson.build
@@ -37,11 +37,10 @@ revision = libgit2_glib_interface_age
 libversion = '@0@.@1@.@2@'.format(soversion, current, revision)
 
 libgit2_glib_prefix = get_option('prefix')
-libgit2_glib_libdir = join_paths(libgit2_glib_prefix, get_option('libdir'))
-libgit2_glib_includedir = join_paths(libgit2_glib_prefix, get_option('includedir'))
-libgit2_glib_datadir = join_paths(libgit2_glib_prefix, get_option('datadir'))
+libgit2_glib_libdir = get_option('libdir')
+libgit2_glib_datadir = get_option('datadir')
 
-libgit2_glib_pkgincludedir = join_paths(libgit2_glib_includedir, libgit2_glib_api_name, meson.project_name())
+libgit2_glib_pkgincludedir = join_paths(get_option('includedir'), libgit2_glib_api_name, 
meson.project_name())
 
 gnome = import('gnome')
 pkg = import('pkgconfig')
diff --git a/meson_python_compile.py b/meson_python_compile.py
index 8aff82c..1fa54ff 100644
--- a/meson_python_compile.py
+++ b/meson_python_compile.py
@@ -5,7 +5,9 @@ import subprocess
 import sys
 
 if not os.environ.get('DESTDIR'):
-  libdir = sys.argv[1]
+  prefix = os.environ['MESON_INSTALL_PREFIX']
+
+  libdir = os.path.join(prefix, sys.argv[1])
 
   print('Byte-compiling python modules...')
   subprocess.call(['python', '-m', 'compileall', '-f', '-q', libdir])
diff --git a/meson_vapi_link.py b/meson_vapi_link.py
index 435cd95..eb64fd6 100644
--- a/meson_vapi_link.py
+++ b/meson_vapi_link.py
@@ -4,10 +4,7 @@ import os
 import subprocess
 import sys
 
-vapidir = os.path.join(sys.argv[1], 'vala', 'vapi')
-
-destdir = os.environ.get('DESTDIR', '')
-dest_vapidir = os.path.normpath(destdir + os.sep + vapidir)
+vapidir = os.path.join(os.environ['MESON_INSTALL_DESTDIR_PREFIX'], sys.argv[1], 'vala', 'vapi')
 
 # FIXME: meson will not track the creation of these files
 #        https://github.com/mesonbuild/meson/blob/master/mesonbuild/scripts/uninstall.py#L39
@@ -15,7 +12,7 @@ old = 'ggit-1.0'
 new = 'libgit2-glib-1.0'
 
 wd = os.getcwd()
-os.chdir(dest_vapidir)
+os.chdir(vapidir)
 
 for ext in ['vapi', 'deps']:
   src = os.path.join('{}.{}'.format(new, ext))