build: some docs

src/build/Config.zig

@@ -178,7 +178,7 @@ pub fn init(b: *std.Build) !Config {
     config.simd = b.option(
         bool,
         "simd",
-        "Build with SIMD-accelerated code paths. This requires additional build dependencies and adds libc as a runtime dependency, but results in significant performance improvements.",
+        "Build with SIMD-accelerated code paths. Results in significant performance improvements.",
     ) orelse true;
 
     config.wayland = b.option(

src/build/SharedDeps.zig

@@ -650,6 +650,8 @@ fn addGtkNg(
     }
 }
 
+/// Add only the dependencies required for `Config.simd` enbled. This also
+/// adds all the simd source files for compilation.
 pub fn addSimd(
     b: *std.Build,
     m: *std.Build.Module,