Revert "Enable the parallel feature on the cc crate"

This reverts commit 71bf6b6a97.

Using the parallel feature on cc requires Rust 1.61 or higher, see
https://github.com/rust-lang/cc-rs/pull/849

Cargo.lock

@@ -88,7 +88,6 @@ version = "1.0.83"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f1174fb0b6ec23863f8b971027804a42614e347eafb0a95bf0b12cdae21fc4d0"
 dependencies = [
- "jobserver",
  "libc",
 ]
 
@@ -422,15 +421,6 @@ version = "1.0.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "af150ab688ff2122fcef229be89cb50dd66af9e01a4ff320cc137eecc9bacc38"
 
-[[package]]
-name = "jobserver"
-version = "0.1.26"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "936cfd212a0155903bcbc060e316fb6cc7cbf2e1907329391ebadc1fe0ce77c2"
-dependencies = [
- "libc",
-]
-
 [[package]]
 name = "lazy_static"
 version = "1.4.0"

Cargo.toml

@@ -77,7 +77,9 @@ predicates = ">= 2, <= 2.1.1"
 pretty_assertions = "1.3.0"
 
 [build-dependencies]
-cc = { version = "1.0.83", features = ["parallel"] }
+# TODO: enable parallel mode once MSRV hits 1.61, see discussion in
+# https://github.com/rust-lang/cc-rs/pull/849
+cc = "1.0.83"
 rayon = "1.7.0"
 version_check = "0.9.4"