[Sanitizer][Docs] Reformat CMake invocation in docs

This was based on post-commit reviewer feedback in #68636.

Author: boomanaiden154

clang/docs/AddressSanitizer.rst

@@ -32,10 +32,7 @@ for the use/testing of AddressSanitizer:
 
 .. code-block:: console
 
-   cmake -DCMAKE_BUILD_TYPE=Release \
-     -DLLVM_ENABLE_PROJECTS="clang" \
-     -DLLVM_ENABLE_RUNTIMES="compiler-rt" \
-     ../llvm
+   $ cmake -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS="clang" -DLLVM_ENABLE_RUNTIMES="compiler-rt" <path to source>/llvm
 
 Usage
 =====