linker-plugin-lto.md: Convert the rust-clang MxN table to a 2xM table

src/doc/rustc/src/linker-plugin-lto.md

@@ -100,20 +100,20 @@ LLVM. However, the approximation is usually reliable.
 
 The following table shows known good combinations of toolchain versions.
 
-|           |  Clang 7  |  Clang 8  |  Clang 9  |  Clang 10 |
-|-----------|-----------|-----------|-----------|-----------|
-| Rust 1.34 |     ✗     |     ✓     |     ✗     |     ✗     |
-| Rust 1.35 |     ✗     |     ✓     |     ✗     |     ✗     |
-| Rust 1.36 |     ✗     |     ✓     |     ✗     |     ✗     |
-| Rust 1.37 |     ✗     |     ✓     |     ✗     |     ✗     |
-| Rust 1.38 |     ✗     |     ✗     |     ✓     |     ✗     |
-| Rust 1.39 |     ✗     |     ✗     |     ✓     |     ✗     |
-| Rust 1.40 |     ✗     |     ✗     |     ✓     |     ✗     |
-| Rust 1.41 |     ✗     |     ✗     |     ✓     |     ✗     |
-| Rust 1.42 |     ✗     |     ✗     |     ✓     |     ✗     |
-| Rust 1.43 |     ✗     |     ✗     |     ✓     |     ✗     |
-| Rust 1.44 |     ✗     |     ✗     |     ✓     |     ✗     |
-| Rust 1.45 |     ✗     |     ✗     |     ✗     |     ✓     |
-| Rust 1.46 |     ✗     |     ✗     |     ✗     |     ✓     |
+| Rust Version | Clang Version |
+|--------------|---------------|
+| Rust 1.34    |    Clang 8    |
+| Rust 1.35    |    Clang 8    |
+| Rust 1.36    |    Clang 8    |
+| Rust 1.37    |    Clang 8    |
+| Rust 1.38    |    Clang 9    |
+| Rust 1.39    |    Clang 9    |
+| Rust 1.40    |    Clang 9    |
+| Rust 1.41    |    Clang 9    |
+| Rust 1.42    |    Clang 9    |
+| Rust 1.43    |    Clang 9    |
+| Rust 1.44    |    Clang 9    |
+| Rust 1.45    |    Clang 10   |
+| Rust 1.46    |    Clang 10   |
 
 Note that the compatibility policy for this feature might change in the future.