Don't build base with nacl glibc and newlib toolchains

It's unnecessary because nothing appears to depend on it,
and it blocks use of C++11 in base.

The IRT build is still enabled because the IRT is the primary user of base_nacl.
The pnacl_newlib build is still enabled because the remoting client uses it.

BUG=360096
R=thakis@chromium.org,mseaborn@chromium.org

Review URL: https://codereview.chromium.org/540093002

Cr-Commit-Position: refs/heads/master@{#293442}

base/base_nacl.gyp

@@ -20,8 +20,8 @@
             'base_target': 1,
             'nacl_untrusted_build': 1,
             'nlib_target': 'libbase_nacl.a',
-            'build_glibc': 1,
-            'build_newlib': 1,
+            'build_glibc': 0,
+            'build_newlib': 0,
             'build_irt': 1,
             'build_pnacl_newlib': 1,
             'sources': [
@@ -47,7 +47,7 @@
             'nacl_untrusted_build': 1,
             'nlib_target': 'libbase_i18n_nacl.a',
             'build_glibc': 0,
-            'build_newlib': 1,
+            'build_newlib': 0,
             'build_irt': 0,
             'build_pnacl_newlib': 1,
             'sources': [