Add cross-compilation support from MacOS to Windows (#13382)

- Modify `build.rs` to use environment variables instead of `cfg`
directive to make cross-compilation to Windows possible
- Make `embed-resource` a global build-dependency for cross-compilation

Release Notes:

- N/A

crates/gpui/Cargo.toml

@@ -81,6 +81,9 @@ collections = { workspace = true, features = ["test-support"] }
 util = { workspace = true, features = ["test-support"] }
 http = { workspace = true, features = ["test-support"] }
 
+[build-dependencies]
+embed-resource = "2.4"
+
 [target.'cfg(target_os = "macos")'.build-dependencies]
 bindgen = "0.65.1"
 cbindgen = "0.26.0"
@@ -143,9 +146,6 @@ windows.workspace = true
 windows-core = "0.57"
 clipboard-win = "3.1.1"
 
-[target.'cfg(windows)'.build-dependencies]
-embed-resource = "2.4"
-
 [[example]]
 name = "hello_world"
 path = "examples/hello_world.rs"