Show config messages from install-wild, install-mold (#38979)

Follows on from
https://github.com/zed-industries/zed/pull/37717#discussion_r2376739687

@dvdsk suggested this but I didn't get to it in the previous PR.

# Tested

```
; sudo rm /usr/local/bin/wild
; ./script/install-wild
Downloading from https://github.com/davidlattimore/wild/releases/download/0.6.0/wild-linker-0.6.0-x86_64-unknown-linux-gnu.tar.gz
Wild is installed to /usr/local/bin/wild

To make it your default, add or merge these lines into your ~/.cargo/config.toml:

[target.x86_64-unknown-linux-gnu]
linker = "clang"
rustflags = ["-C", "link-arg=--ld-path=wild"]

[target.aarch64-unknown-linux-gnu]
linker = "clang"
rustflags = ["-C", "link-arg=--ld-path=wild"]

```

```
; sudo rm /usr/local/bin/mold
; ./script/install-mold 2.34.0
Downloading from https://github.com/rui314/mold/releases/download/v2.34.0/mold-2.34.0-x86_64-linux.tar.gz
Mold is installed to /usr/local/bin/mold

To make it your default, add or merge these lines into your ~/.cargo/config.toml:

[target.'cfg(target_os = "linux")']
linker = "clang"
rustflags = ["-C", "link-arg=-fuse-ld=mold"]
```

Release Notes:

- N/A

script/linux

@@ -14,17 +14,6 @@ function finalize {
   cat <<EOF
 Note: It's recommended to install and configure Wild or Mold for faster builds.
       Run script/install-wild or script/install-mold.
-      Then add these lines to your ~/.cargo/config.toml:
-
-[target.x86_64-unknown-linux-gnu]
-linker = "clang"
-rustflags = ["-C", "link-arg=--ld-path=wild"]
-
-[target.aarch64-unknown-linux-gnu]
-linker = "clang"
-rustflags = ["-C", "link-arg=--ld-path=wild"]
-
-
 
 Finished installing Linux dependencies with script/linux
 EOF