Fix a broken link, and add link checking to CI.

Author: ehuss

.github/workflows/rbe.yml

@@ -14,7 +14,7 @@ jobs:
     - name: Install Rust
       run: |
         rustup set profile minimal
-        rustup toolchain install stable -c rust-docs
+        rustup toolchain install nightly -c rust-docs
         rustup default nightly
 
     - name: Install mdbook
@@ -35,6 +35,12 @@ jobs:
     - name: Build HTML
       run: mdbook build
 
+    - name: Check for broken links
+      run: |
+        curl -sSLo linkcheck.sh \
+          https://raw.githubusercontent.com/rust-lang/rust/master/src/tools/linkchecker/linkcheck.sh
+        sh linkcheck.sh --all rust-by-example
+
     - name: Upload Artifact
       uses: actions/upload-artifact@v1
       with:

src/unsafe/asm.md

@@ -285,7 +285,9 @@ assert_eq!(x, 4 * 6);
 
 ## Symbol operands and ABI clobbers
 
-By default, `asm!` assumes that any register not specified as an output will have its contents preserved by the assembly code. The [`clobber_abi`](#abi-clobbers) argument to `asm!` tells the compiler to automatically insert the necessary clobber operands according to the given calling convention ABI: any register which is not fully preserved in that ABI will be treated as clobbered.  Multiple `clobber_abi` arguments may be provided and all clobbers from all specified ABIs will be inserted.
+By default, `asm!` assumes that any register not specified as an output will have its contents preserved by the assembly code. The [`clobber_abi`] argument to `asm!` tells the compiler to automatically insert the necessary clobber operands according to the given calling convention ABI: any register which is not fully preserved in that ABI will be treated as clobbered.  Multiple `clobber_abi` arguments may be provided and all clobbers from all specified ABIs will be inserted.
+
+[`clobber_abi`]: ../../reference/inline-assembly.html#abi-clobbers
 
 ```rust
 use std::arch::asm;