Install rust on readthedocs

Makefile

@@ -139,4 +139,11 @@ ssh-submodule-urls:
 		echo -n 'New URL: '; \
 		git remote get-url origin"
 
+install-rust:
+	curl https://sh.rustup.rs -sSf | sh -s -- -y
+
+rust-ext:
+	[ "$$READTHEDOCS" != "True" ] || $(MAKE) install-rust
+	cd ./rust && PATH="$$HOME/.cargo/bin/:$$PATH" cargo build --release
+
 .PHONY: docs

scripts/travis-install.sh

@@ -9,5 +9,5 @@ if [ "$TRAVIS_OS_NAME" = "osx" ]; then
     . $HOME/osx-py3/bin/activate
 fi
 
-curl https://sh.rustup.rs -sSf | sh -s -- -y
+make install-rust
 export PATH="$HOME/.cargo/bin/:$PATH"

setup.py

@@ -40,16 +40,16 @@ requirements = [
 
 def build_native(spec):
     build = spec.add_external_build(
-        cmd=['cargo', 'build', '--release'],
-        path='./rust'
+        cmd=['make', 'rust-ext'],
+        path='.'
     )
 
     spec.add_cffi_module(
         module_path='vdirsyncer._native',
         dylib=lambda: build.find_dylib(
-            'vdirsyncer_rustext', in_path='target/release'),
+            'vdirsyncer_rustext', in_path='rust/target/release'),
         header_filename=lambda: build.find_header(
-            'vdirsyncer_rustext.h', in_path='target'),
+            'vdirsyncer_rustext.h', in_path='rust/target'),
         # Rust bug: If thread-local storage is used, this flag is necessary
         # (mitsuhiko)
         rtld_flags=['NODELETE']