add linux32 to i686 builds (#338)

* add linux32 to i686 builds

* Add test. Fix bug with space.

* Apply suggestions from code review

apply suggestions

Co-authored-by: Joe Rickerby <joerick@mac.com>

* change uname to platform.machine

Co-authored-by: Joe Rickerby <joerick@mac.com>

cibuildwheel/linux.py

@@ -109,6 +109,7 @@ def build(options: BuildOptions):
         container_name = 'cibuildwheel-{}'.format(uuid.uuid4())
 
         try:
+            shell_cmd = ['linux32', '/bin/bash'] if platform_tag.endswith("i686") else ['/bin/bash']
             call(['docker', 'create',
                   '--env', 'CIBUILDWHEEL',
                   '--name', container_name,
@@ -136,7 +137,7 @@ def build(options: BuildOptions):
                         )
 
                 call(
-                    ['docker', 'exec', '-i', container_name, '/bin/bash'],
+                    ['docker', 'exec', '-i', container_name] + shell_cmd,
                     universal_newlines=True,
                     input='''
                         # give xtrace output an extra level of indent inside docker

test/02_test/test/spam_test.py

@@ -1,6 +1,8 @@
 from __future__ import print_function
 import os
+import platform
 import sys
+import struct
 from unittest import TestCase
 
 import spam
@@ -43,3 +45,12 @@ class TestSpam(TestCase):
             print("=[listdir]2", os.listdir(os.path.join(virtualenv_path, 'bin')))
         self.assertTrue(path_contains(virtualenv_path, sys.executable))
         self.assertTrue(path_contains(virtualenv_path, spam.__file__))
+
+    def test_uname(self):
+        if platform.system() == "Windows":
+            return
+        # if we're running in 32-bit Python, check that the machine is i686.
+        # See #336 for more info.
+        bits = struct.calcsize("P") * 8
+        if bits == 32:
+            self.assertEqual(platform.machine(), "i686")