Re-enable BUILD_TESTS for fbcode_builder

Summary: As it turns out, several of the `fizz` dependencies require it to have been built with tests enabled, so it's just easier to build them always, IIRC they only waste 1-2 minutes of time.

Reviewed By: lnicco

Differential Revision: D17837758

fbshipit-source-id: dd0c73b3aaf72831ce702dbcecd4e3ff627a4901

build/fbcode_builder/specs/fizz.py

@@ -10,12 +10,13 @@ import specs.sodium as sodium
 
 
 def fbcode_builder_spec(builder):
-    # Projects that **depend** on fizz should don't need to build tests.
     builder.add_option(
         'fizz/fizz/build:cmake_defines',
         {
-            # This is set to ON in the fizz `fbcode_builder_config.py` 
-            'BUILD_TESTS': 'OFF',
+            # Fizz's build is kind of broken, in the sense that both `mvfst`
+            # and `proxygen` depend on files that are only installed with
+            # `BUILD_TESTS` enabled, e.g. `fizz/crypto/test/TestUtil.h`.
+            'BUILD_TESTS': 'ON',
         }
     )
     return {