Also namespace target/man -> target/fish-man

If cargo ever wants to write to "target/man", it would collide with our
use of this path.  Let's make this less likely by prefixing the name with
"fish-".  This also makes it more obvious that this is fish's invention.

build.rs

@@ -46,7 +46,7 @@ fn main() {
 
     std::env::set_var("FISH_BUILD_VERSION", version);
 
-    let targetman = cargo_target_dir.join("man");
+    let targetman = cargo_target_dir.join("fish-man");
 
     #[cfg(feature = "embed-data")]
     #[cfg(not(clippy))]

src/builtins/status.rs

@@ -322,7 +322,7 @@ fn parse_cmd_opts(
 
 #[cfg(feature = "embed-data")]
 #[derive(RustEmbed)]
-#[folder = "target/man/man1"]
+#[folder = "target/fish-man/man1"]
 #[prefix = "man/man1/"]
 struct Docs;