Revert limiting codegen units

Author: calebzulawski

.travis.yml

@@ -13,17 +13,16 @@ matrix:
     - name: "aarch64-unknown-linux-gnu (neon)"
       os: linux
       arch: arm64
-      env: RUSTFLAGS=-Ccodegen-units=1
 
     - name: "aarch64-unknown-linux-gnu (neon, sve)"
       os: linux
       arch: arm64
-      env: RUSTFLAGS="-Ctarget-feature=+sve -Ccodegen-units=1
+      env: RUSTFLAGS=-Ctarget-feature=+sve
 
     - name: "aarch64-unknown-linux-gnu (native, see log for cfg)"
       os: linux
       arch: arm64
-      env: RUSTFLAGS="-Ctarget-cpu=native -Ccodegen-units=1"
+      env: RUSTFLAGS=-Ctarget-cpu=native
 
     # Linux (powerpc64le)
     - name: "powerpc64le-unknown-linux-gnu (altivec, vsx, power8-*)"