Lower the MSRV to 1.63

This will get us compatibility with Debian stable.

If this turns out to be problematic, we can always raise it back in the
time before 1.0 is released.

.github/workflows/full_ci.yml

@@ -154,7 +154,7 @@ jobs:
           stable,
           beta,
           nightly,
-          1.71.0,
+          1.63.0,
         ]
     steps:
       - uses: actions/checkout@v4
@@ -179,7 +179,7 @@ jobs:
           - { toolchain: stable, os: macos-14 }
           - { toolchain: beta, os: macos-14 }
           - { toolchain: nightly, os: macos-14 }
-          - { toolchain: 1.71.0, os: macos-14 }
+          - { toolchain: 1.63.0, os: macos-14 }
     runs-on: ${{ matrix.target.os }}
     steps:
       - uses: actions/checkout@v4
@@ -200,7 +200,7 @@ jobs:
       fail-fast: true
       matrix:
         toolchain: [
-          1.71.0,
+          1.63.0,
           stable,
         ]
     steps:

Cargo.toml

@@ -14,7 +14,7 @@ exclude = ["/ci/*", "/.github/*", "/.cirrus.yml", "/triagebot.toml"]
 description = """
 Raw FFI bindings to platform libraries like libc.
 """
-rust-version = "1.71.0"
+rust-version = "1.63.0"
 
 [package.metadata.docs.rs]
 features = ["const-extern-fn", "extra_traits"]

README.md

@@ -52,7 +52,7 @@ libc = "0.2"
 
 ## Rust version support
 
-The minimum supported Rust toolchain version is currently **Rust 1.71.0**
+The minimum supported Rust toolchain version is currently **Rust 1.63.0**
 (libc does not currently have any policy regarding changes to the minimum
 supported Rust version; such policy is a work in progress).