Demo: Add override_rustc_flags

This makes it possible to do platform specific flags, needed e.g. in
value-bag to compile both for WASM and non-WASM. Usage example:

[package.metadata.raze.crates.value-bag.'1.0.0-alpha.8']
gen_buildrs = false
override_rustc_flags = """
    [ "--cap-lints=allow" ] +
    selects.with_or({
        (
            "@rules_rust//rust/platform:wasm32-unknown-unknown",
        ): ["--cfg=value_bag_capture_fallback"],
        "//conditions:default": ["--cfg=value_bag_capture_ctor"],
    })
"""

impl/BUILD.bazel

@@ -1,4 +1,4 @@
-load("@rules_rust//rust:rust.bzl", "rust_binary", "rust_library", "rust_test")
+load("@rules_rust//rust:defs.bzl", "rust_binary", "rust_library", "rust_test")
 load("//third_party/cargo:crates.bzl", "all_crate_deps")
 
 package(default_visibility = ["//visibility:public"])

impl/src/rendering/templates/partials/common_attrs.template

@@ -44,14 +44,18 @@
         {%- endfor %}
     },
     {%- endif %}
+    {%- if crate.raze_settings.override_rustc_flags %}
+    rustc_flags = {{crate.raze_settings.override_rustc_flags}},
+    {%- else %}
     rustc_flags = [
         "--cap-lints=allow",
         {%- for flag in crate.raze_settings.additional_flags %}
         "{{flag}}",
         {%- endfor %}
     ],
+    {%- endif %}
     tags = [
         "cargo-raze",
         "manual",
     ],
-    version = "{{ crate.pkg_version }}",
+    version = "{{ crate.pkg_version }}",

impl/src/settings.rs

@@ -159,6 +159,10 @@ pub struct CrateSettings {
   #[serde(default)]
   pub additional_flags: Vec<String>,
 
+  /// Escape hatch for override value for rustc_flags, make sure to include "--cap-lints=allow"
+  #[serde(default)]
+  pub override_rustc_flags: Option<String>,
+
   /// Environment variables to be added to the crate compilation process.
   #[serde(default)]
   pub additional_env: BTreeMap<String, String>,
@@ -274,6 +278,7 @@ impl Default for CrateSettings {
       build_data_dependencies: Vec::new(),
       buildrs_additional_deps: Vec::new(),
       buildrs_additional_environment_variables: BTreeMap::new(),
+      override_rustc_flags: None,
       patch_args: Vec::new(),
       patch_cmds: Vec::new(),
       patch_cmds_win: Vec::new(),