Allow setting needsPic crosstool capability using feature

`needsPic` can now be expressed using 'pic' feature (should be enabled for it to take effect).

This cl is a step towards https://github.com/bazelbuild/bazel/issues/5883. Also
see the rollout doc here:
https://docs.google.com/document/d/1uv4c1zag6KvdI31qdx8C6jiTognXPQrxgsUpVefm9fM/edit#.

Flag removing legacy behavior is https://github.com/bazelbuild/bazel/issues/6861

RELNOTES: None.
PiperOrigin-RevId: 227134726
diff --git a/third_party/com/github/bazelbuild/bazel/src/main/protobuf/crosstool_config.proto b/third_party/com/github/bazelbuild/bazel/src/main/protobuf/crosstool_config.proto
index f275b20..9aa059f 100644
--- a/third_party/com/github/bazelbuild/bazel/src/main/protobuf/crosstool_config.proto
+++ b/third_party/com/github/bazelbuild/bazel/src/main/protobuf/crosstool_config.proto
@@ -373,6 +373,7 @@
   optional bool supports_fission = 43 [default = false];
   // Legacy field, ignored by Bazel.
   optional bool supports_dsym = 51 [default = false];
+  // Legacy field, use 'supports_pic' feature instead
   optional bool needsPic = 12 [default = false];
 
   // Compiler flags for C/C++/Asm compilation.