Bug 1527797 - Relax rust build dependency for --enable-project=tools/crashreporter. r=dmajor

The tools/crashreporter project only builds one crate, that rarely
changes, and currently builds with rustc 1.22.

Differential Revision: https://phabricator.services.mozilla.com/D19756

build/moz.configure/rust.configure

@@ -54,9 +54,9 @@ def cargo_info(cargo):
     )
 
 
-@depends(rustc_info, cargo_info)
+@depends(rustc_info, cargo_info, build_project)
 @imports(_from='textwrap', _import='dedent')
-def rust_compiler(rustc_info, cargo_info):
+def rust_compiler(rustc_info, cargo_info, build_project):
     if not rustc_info:
         die(dedent('''\
         Rust compiler not found.
@@ -66,8 +66,12 @@ def rust_compiler(rustc_info, cargo_info):
         You can install rust by running './mach bootstrap'
         or by directly running the installer from https://rustup.rs/
         '''))
-    rustc_min_version = Version('1.32.0')
-    cargo_min_version = rustc_min_version
+    if build_project == 'tools/crashreporter':
+        rustc_min_version = Version('1.22.0')
+        cargo_min_version = Version('0.23.0')
+    else:
+        rustc_min_version = Version('1.32.0')
+        cargo_min_version = rustc_min_version
 
     version = rustc_info.version
     if version < rustc_min_version: