Add separate extra_deps and omit_deps fixups for build scripts

Summary:
It is goofy that when you use `extra_deps` in a fixup, those deps get applied to **both** the library/binary and to its build script. There is almost never a case you would want to add an identical dependency to both a library/binary and its build script. And in the worse case, this makes `extra_deps` completely unusable, such as when you want to add a platform-specific dependency (e.g. Android) which is incompatible with your execution platform.

Since {D73977930} there is a dedicated section for controlling the build-script build. This diff adds support for `extra_deps` and `omit_deps` in that section, and changes top-level `extra_deps` and `omit_deps` to no longer apply to build scripts.

```lang=toml
omit_deps = ["example"]
extra_deps = [":better-example"]

[buildscript.build]
omit_deps = ["example"]
extra_deps = [":better-example"]
```

Reviewed By: JakobDegen

Differential Revision: D74158951

fbshipit-source-id: cc1e8865cbcccecf6b6e2791942e61bfdd88b8e7

Author: David Tolnay

src/fixups.rs

@@ -727,9 +727,14 @@ impl<'meta> Fixups<'meta> {
         // Pre-compute the list of all filtered dependencies. If a platform filters a dependency
         // added by the base, we need to filter it from the base and add it to all other platforms.
         for (platform, fixup) in self.fixup_config.configs(&self.package.version) {
+            let fixup_omit_deps = if self.target.crate_bin() && self.target.kind_custom_build() {
+                &fixup.buildscript.build.omit_deps
+            } else {
+                &fixup.omit_deps
+            };
             let platform_omits = omits.entry(platform).or_insert_with(HashSet::new);
-            platform_omits.extend(fixup.omit_deps.iter().map(String::as_str));
-            all_omits.extend(fixup.omit_deps.iter().map(String::as_str));
+            platform_omits.extend(fixup_omit_deps.iter().map(String::as_str));
+            all_omits.extend(fixup_omit_deps.iter().map(String::as_str));
         }
 
         for ResolvedDep {
@@ -819,7 +824,12 @@ impl<'meta> Fixups<'meta> {
         }
 
         for (platform, config) in self.fixup_config.configs(&self.package.version) {
-            ret.extend(config.extra_deps.iter().map(|dep| {
+            let fixup_extra_deps = if self.target.crate_bin() && self.target.kind_custom_build() {
+                &config.buildscript.build.extra_deps
+            } else {
+                &config.extra_deps
+            };
+            ret.extend(fixup_extra_deps.iter().map(|dep| {
                 (
                     None,
                     RuleRef::new(dep.to_string()).with_platform(platform),

src/fixups/buildscript.rs

@@ -6,6 +6,7 @@
  */
 
 use std::collections::BTreeMap;
+use std::collections::BTreeSet;
 use std::fmt;
 use std::path::PathBuf;
 
@@ -47,6 +48,10 @@ pub struct BuildscriptBuild {
     #[serde(default)]
     pub env: BTreeMap<String, String>,
     pub link_style: Option<String>,
+    #[serde(default)]
+    pub extra_deps: BTreeSet<String>,
+    #[serde(default)]
+    pub omit_deps: BTreeSet<String>,
     #[serde(skip_deserializing)]
     pub defaulted_to_empty: bool,
 }
@@ -56,6 +61,8 @@ impl Default for BuildscriptBuild {
         BuildscriptBuild {
             env: BTreeMap::new(),
             link_style: None,
+            extra_deps: BTreeSet::new(),
+            omit_deps: BTreeSet::new(),
             defaulted_to_empty: true,
         }
     }