Rollup merge of rust-lang#143961 - 1c3t3a:correct-exploit-mitigations, r=rcvalle

Correct which exploit mitigations are enabled by default

This was brought up by `@Noratrieb` in [#project-exploit-mitigations > Incorrect table in the rustc book](https://rust-lang.zulipchat.com/#narrow/channel/343119-project-exploit-mitigations/topic/Incorrect.20table.20in.20the.20rustc.20book/with/523684203). Thanks! :)

[Rendered](https://github.com/rust-lang/rust/blob/132a47e72316b60e99c3e5fefb9c3a06641138e4/src/doc/rustc/src/exploit-mitigations.md)

r? `@rcvalle`

Author: matthiaskrgr

src/doc/rustc/src/exploit-mitigations.md

@@ -54,17 +54,17 @@ Summary of exploit mitigations supported by the Rust compiler when building
 programs for the Linux operating system on the AMD64 architecture and
 equivalent.
 
-| Exploit mitigation | Supported and enabled by default | Since |
-| - | - | - |
-| Position-independent executable | Yes | 0.12.0 (2014-10-09) |
-| Integer overflow checks | Yes (enabled when debug assertions are enabled, and disabled when debug assertions are disabled) | 1.1.0 (2015-06-25) |
-| Non-executable memory regions | Yes | 1.8.0 (2016-04-14) |
-| Stack clashing protection | Yes | 1.20.0 (2017-08-31) |
-| Read-only relocations and immediate binding | Yes | 1.21.0 (2017-10-12) |
-| Heap corruption protection | Yes | 1.32.0 (2019-01-17) (via operating system default or specified allocator) |
-| Stack smashing protection | Yes | Nightly |
-| Forward-edge control flow protection | Yes | Nightly |
-| Backward-edge control flow protection (e.g., shadow and safe stack) | Yes | Nightly |
+| Exploit mitigation | Supported | Enabled by default | Since |
+| - | - | - | - |
+| Position-independent executable | Yes | Yes | 0.12.0 (2014-10-09) |
+| Integer overflow checks | Yes | (enabled when debug assertions are enabled, and disabled when debug assertions are disabled) | 1.1.0 (2015-06-25) |
+| Non-executable memory regions | Yes | Yes | 1.8.0 (2016-04-14) |
+| Stack clashing protection | Yes | Yes | 1.20.0 (2017-08-31) |
+| Read-only relocations and immediate binding | Yes | Yes | 1.21.0 (2017-10-12) |
+| Heap corruption protection | Yes | Yes | 1.32.0 (2019-01-17) (via operating system default or specified allocator) |
+| Stack smashing protection | Yes | No, `-Z stack-protector` | Nightly |
+| Forward-edge control flow protection | Yes | No, `-Z sanitizer=cfi` | Nightly |
+| Backward-edge control flow protection (e.g., shadow and safe stack) | Yes | No, `-Z sanitizer=shadow-call-stack,safestack` | Nightly |
 
 [^all-targets]: See <https://github.com/rust-lang/rust/tree/master/compiler/rustc_target/src/spec>
     for a list of targets and their default options.