[PATCH 3 of 3] rust: switched to 'cargo rustc' in setup.py

[Georges Racinet]

# HG changeset patch
# User Georges Racinet <georges.racinet at octobus.net>
# Date 1558045063 -7200
#      Fri May 17 00:17:43 2019 +0200
# Node ID 1bd9227bf68db22ce48ab381c4d26d4c71edca42
# Parent  2cbfd089a1ce0ec46f9e124e0574e74491fa4788
# EXP-Topic rust-build-platforms
rust: switched to 'cargo rustc' in setup.py

This is more flexible in the passing of additional flags, also
what setuptools_rust does, giving less uncertainty about non-Linux
platforms.

diff -r 2cbfd089a1ce -r 1bd9227bf68d setup.py
--- a/setup.py	Fri Jun 14 11:18:06 2019 +0100
+++ b/setup.py	Fri May 17 00:17:43 2019 +0200
@@ -1195,13 +1195,14 @@
             import pwd
             env['HOME'] = pwd.getpwuid(os.getuid()).pw_dir
 
-        cargocmd = ['cargo', 'build', '-vv', '--release']
+        cargocmd = ['cargo', 'rustc', '-vv', '--release']
         if sys.version_info[0] == 3 and self.py3_features is not None:
             cargocmd.extend(('--features', self.py3_features,
                              '--no-default-features'))
+        cargocmd.append('--')
         if sys.platform == 'darwin':
-            env['RUSTFLAGS'] = ("-C link-arg=-undefined "
-                                "-C link-arg=dynamic_lookup")
+            cargocmd.extend(("-C", "link-arg=-undefined",
+                             "-C", "link-arg=dynamic_lookup"))
         try:
             subprocess.check_call(cargocmd, env=env, cwd=self.rustsrcdir)
         except OSError as exc: