libarchive-sys-provided: let user override paths

let the user override assumed paths via environment.
lib_dir is probed first from LD_LIBRARY_PATH.
Path to libarchive can be specified via LIBARCHIVE environment variable.
If not found it falls back to lib_dir/libarchive.so.

With this patch it possible to run scancode is buildsystems like YOCTO,
which heaviily rely on overriding paths via environment to pick the
correct implementation from the build workspace

Signed-off-by: Konrad Weihmann <kweihmann@outlook.com>

Author: priv-kweihmann

builtins/extractcode_libarchive_system_provided/src/extractcode_libarchive/__init__.py

@@ -7,8 +7,9 @@
 # See https://aboutcode.org for more information about nexB OSS projects.
 #
 
-from os import path
 import platform
+from os import environ
+from os import path
 
 from plugincode.location_provider import LocationProviderPlugin
 
@@ -20,30 +21,33 @@ def get_locations(self):
         locations of the libarchive shared library as installed on various Linux
         distros or on FreeBSD.
         """
-        system_arch = platform.machine()
-        mainstream_system = platform.system().lower()
-        if mainstream_system == 'linux':
-            distribution = platform.linux_distribution()[0].lower()
-            debian_based_distro = ['ubuntu', 'mint', 'debian']
-            rpm_based_distro = ['fedora', 'redhat']
-
-            if distribution in debian_based_distro:
-                lib_dir = '/usr/lib/'+system_arch+'-linux-gnu'
-
-            elif distribution in rpm_based_distro:
-                lib_dir = '/usr/lib64'
-
-            else:
-                raise Exception('Unsupported system: {}'.format(distribution))
-
-        elif mainstream_system == 'freebsd':
-            if path.isdir('/usr/local/'):
-                lib_dir = '/usr/local/lib'
-            else:
-                lib_dir = '/usr/lib'
+        lib_dir = environ.get('LD_LIBRARY_PATH')
+        if not lib_dir:
+            system_arch = platform.machine()
+            mainstream_system = platform.system().lower()
+            if mainstream_system == 'linux':
+                distribution = platform.linux_distribution()[0].lower()
+                debian_based_distro = ['ubuntu', 'mint', 'debian']
+                rpm_based_distro = ['fedora', 'redhat']
+
+                if distribution in debian_based_distro:
+                    lib_dir = '/usr/lib/'+system_arch+'-linux-gnu'
+
+                elif distribution in rpm_based_distro:
+                    lib_dir = '/usr/lib64'
+
+                else:
+                    raise Exception('Unsupported system: {}'.format(distribution))
+
+            elif mainstream_system == 'freebsd':
+                if path.isdir('/usr/local/'):
+                    lib_dir = '/usr/local/lib'
+                else:
+                    lib_dir = '/usr/lib'
+        lib_archive = environ.get('LIBARCHIVE', path.join(lib_dir, 'libarchive.so'))
 
         locations = {
             'extractcode.libarchive.libdir': lib_dir,
-            'extractcode.libarchive.dll': path.join(lib_dir, 'libarchive.so'),
+            'extractcode.libarchive.dll': lib_archive,
         }
         return locations