[gobject-introspection] scanner: Fix library lookup under MinGW without libtool

[Christoph Reiter <creiter src gnome org>]

commit e56d70da837bd309bf8cddbce309a5a773e098b6
Author: Christoph Reiter <reiter christoph gmail com>
Date:   Mon Jan 22 11:20:49 2018 +0100

    scanner: Fix library lookup under MinGW without libtool
    
    When executing the scanner binary use the PATH/LIB env vars
    also under MinGW, since LD_LIBRARY_PATH/rpath doesn't work there.
    
    When resolving the library name from the import library look into
    the user provided library paths first before falling back to the
    default gcc search path.
    
    This fixes the gir/typelib generation for meson under MSYS2.
    Note that MSYS2 ships various patches, so this might not fix it
    for all MinGW users.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=791902

 giscanner/ccompiler.py |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/giscanner/ccompiler.py b/giscanner/ccompiler.py
index 29de0ee..a8bd5b1 100644
--- a/giscanner/ccompiler.py
+++ b/giscanner/ccompiler.py
@@ -116,7 +116,7 @@ class CCompiler(object):
         runtime_path_envvar = []
         runtime_paths = []
 
-        if self.check_is_msvc():
+        if os.name == 'nt':
             runtime_path_envvar = ['LIB', 'PATH']
         else:
             runtime_path_envvar = ['LD_LIBRARY_PATH']
@@ -288,9 +288,10 @@ class CCompiler(object):
             proc = subprocess.Popen([self.compiler_cmd, '-print-search-dirs'],
                                     stdout=subprocess.PIPE)
             o, e = proc.communicate()
+            libsearch = options.library_paths
             for line in o.decode('ascii').splitlines():
                 if line.startswith('libraries: '):
-                    libsearch = line[len('libraries: '):].split(os.pathsep)
+                    libsearch += line[len('libraries: '):].split(os.pathsep)
 
         shlibs = []
         not_resolved = []