Fixed bdist_wheel not lower casing the platform tag (#366)

Fixes #364.

Author: agronholm

docs/news.rst

@@ -1,6 +1,11 @@
 Release Notes
 =============
 
+**UNRELEASED**
+
+- Fixed ``bdist_wheel`` not working on FreeBSD due to mismatching platform tag
+  name (it was not being converted to lowercase)
+
 **0.35.0 (2020-08-13)**
 
 - Switched to the packaging_ library for computing wheel tags

src/wheel/bdist_wheel.py

@@ -254,7 +254,7 @@ def get_tag(self):
             if plat_name in ('linux-x86_64', 'linux_x86_64') and sys.maxsize == 2147483647:
                 plat_name = 'linux_i686'
 
-        plat_name = plat_name.replace('-', '_').replace('.', '_')
+        plat_name = plat_name.lower().replace('-', '_').replace('.', '_')
 
         if self.root_is_pure:
             if self.universal: