Reland "Make compiler/optimizing/ symbols hidden."

This reverts commit 0a51605ddd81635135463dab08b6f7c21b58ffb0.

Reason for revert: Reland after some of the required work
was merged in other CLs.

Also address a TODO from the original CL to mark required
symbols with EXPORT in `intrinsic_objects.h`.

Also mark symbols in new files as HIDDEN.

Bug: 186902856
Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Change-Id: I936d448983928af23614ca82c2d0bf9a645e2c52
diff --git a/tools/generate_operator_out.py b/tools/generate_operator_out.py
index f1491d8..f3de61c 100755
--- a/tools/generate_operator_out.py
+++ b/tools/generate_operator_out.py
@@ -65,7 +65,7 @@
                     continue
 
                 # Is this the start or end of a namespace?
-                m = re.search(r'^namespace (\S+) \{', raw_line)
+                m = re.search(r'^namespace (\S+) (HIDDEN |EXPORT )?\{', raw_line)
                 if m:
                     namespaces.append(m.group(1))
                     continue