dev-lang/rust: fix network-less builds

When building without a network connection or FEATURES=network-sandbox
the build would fail due to the build process reaching out to the
internet to fetch down some files that the package manager already got
for it. This neuters that network access and uses the existing files.

Signed-off-by: Doug Goldstein <[email protected]>

dev-lang/rust/files/rust-1.12.0-disable-fetching-stage0.patch

@@ -0,0 +1,36 @@
+From b6a4c78ef7b4bc6c32145f27e8a679d5baf36f90 Mon Sep 17 00:00:00 2001
+From: Doug Goldstein <[email protected]>
+Date: Mon, 24 Oct 2016 00:01:37 -0500
+Subject: [PATCH] disable fetching stage0 and use whats there
+
+In Gentoo and Yocto alike we do not allow build environments network
+access and as a result the package manager is responsible for fetching
+down all the files necessary. In both they are configured to fetch down
+the compiler and unpack it and place the stage0 tarball inside of the
+'dl' directory for the build system to use. Unfortunately it
+unconditionally attempts to fetch down the files and ignores what is
+already available so this avoids that behavior and just uses what's in
+the 'dl' directory.
+
+Upstream-Status: Not upstreamable
+Signed-off-by: Doug Goldstein <[email protected]>
+---
+ src/etc/get-stage0.py | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/src/etc/get-stage0.py b/src/etc/get-stage0.py
+index 127251c..2889c07 100644
+--- a/src/etc/get-stage0.py
++++ b/src/etc/get-stage0.py
+@@ -31,7 +31,7 @@ def main(triple):
+ filename = 'rustc-{}-{}.tar.gz'.format(channel, triple)
+ url = 'https://static.rust-lang.org/dist/{}/{}'.format(date, filename)
+ dst = dl_dir + '/' + filename
+- bootstrap.get(url, dst)
++ #bootstrap.get(url, dst)
+
+ stage0_dst = triple + '/stage0'
+ if os.path.exists(stage0_dst):
+-- 
+2.7.3
+

dev-lang/rust/rust-1.12.0.ebuild

@@ -55,6 +55,8 @@ PDEPEND=">=app-eselect/eselect-rust-0.3_pre20150425"
 
 S="${WORKDIR}/${MY_P}"
 
+PATCHES=("${FILESDIR}/rust-1.12.0-disable-fetching-stage0.patch")
+
 src_unpack() {
  unpack "rustc-${PV}-src.tar.gz" || die
  mkdir "${MY_P}/dl" || die

dev-lang/rust/rust-1.12.1.ebuild

@@ -55,6 +55,8 @@ PDEPEND=">=app-eselect/eselect-rust-0.3_pre20150425"
 
 S="${WORKDIR}/${MY_P}"
 
+PATCHES=("${FILESDIR}/rust-1.12.0-disable-fetching-stage0.patch")
+
 src_unpack() {
  unpack "rustc-${PV}-src.tar.gz" || die
  mkdir "${MY_P}/dl" || die