Fix bazel build (#592)

Signed-off-by: Shameek Ganguly <[email protected]>

Author: shameekganguly

graphics/BUILD.bazel

@@ -21,6 +21,8 @@ public_headers_no_gen = glob([
     "include/gz/common/**/*.hh",
 ])
 
+private_headers = glob(["src/VHACD/*.h"])
+
 sources = glob(
     ["src/*.cc"],
     exclude = ["src/*_TEST.cc"],
@@ -51,7 +53,7 @@ public_headers = public_headers_no_gen + [
 
 cc_library(
     name = "graphics",
-    srcs = sources,
+    srcs = sources + private_headers,
     hdrs = public_headers,
     copts = [
         "-Wno-implicit-fallthrough",