rustc: Update from version 1.16.0 to 1.21.0

needed for Firefox
revision 1: build with cargo and snapshot system
revision 2: rebuild with system rustc

rustc.be0

@@ -1,6 +1,6 @@
 #!/usr/bin/env beesh
 
-# BEE_VERSION rustc-1.16.0-0
+# BEE_VERSION rustc-1.21.0-2
 
 SRCURL[0]="https://static.rust-lang.org/dist/rustc-${PKGVERSION}-src.tar.gz"
 
@@ -26,11 +26,17 @@ export RUST_BACKTRACE=1
 mee_configure() {
     #rust creates .cargo dir in your home
     export HOME=${S}
-    ${S}/configure --prefix=${PREFIX}
+    ${S}/configure --prefix=${PREFIX} \
+                   --mandir=${MANDIR} \
+                   --libdir=${LIBDIR} \
+                   --enable-local-rust \
+                   --disable-rpath \
+                   --enable-extended \
+                   --disable-codegen-tests
 }
 
 mee_build() {
-    start_cmd make ${BEE_MAKEFLAGS}
+    CC=clang CXX=clang++ start_cmd make ${BEE_MAKEFLAGS}
 }
 
 mee_install() {