This is a hack that, combined with g-ir-scanner-wrapper, allows us to put
/usr/lib inside LD_LIBRARY_PATH before all the other paths that g-ir-scanner
appends. This is very important, because if we don't put /usr/lib first, the
cross base will be first and during certain circumstances (musl, cross-endian)
the compiler will fail to execute.

We cannot use another way to append it, because we don't want to put /usr/lib
inside the library paths for scanning - we don't want the gi scanner to
process any of these libs. We just want the native executables to run
correctly.

As for using the literal LD_LIBRARY_PATH inside the environment - the scanner
will actually read it, but it will put it at the *end*, which does not help
us.

Ping 'q66 <daniel@octaforge.org>' for any questions.

--- a/giscanner/ccompiler.py
+++ b/giscanner/ccompiler.py
@@ -180,6 +180,7 @@ class CCompiler(object):
 
         runtime_path_envvar = []
         runtime_paths = []
+        extra_ld_libpath = 'GI_SCANNER_EXTRA_LD_LIBRARY_PATH'
 
         if os.name == 'nt':
             runtime_path_envvar = ['LIB', 'PATH']
@@ -234,6 +235,12 @@ class CCompiler(object):
             else:
                 os.environ[envvar] = os.pathsep.join(runtime_paths)
 
+            # extra paths to prepend, for cross-compiling
+            if extra_ld_libpath in os.environ:
+                os.environ[envvar] = os.pathsep.join([
+                    os.environ[extra_ld_libpath], os.environ[envvar]
+                ])
+
     def get_external_link_flags(self, args, libraries):
         # An "external" link is where the library to be introspected
         # is installed on the system; this case is used for the scanning