Small refactor of base_nacl.gyp

1) Now, native_client/src/public/linux_syscalls are included
automatically during the PNaCl toolchain's build for Non-SFI.
So, it is not necessary to add it for each target.
2) <(DEPTH) is replaced by .. as relative path is preferred.
3) Sort dependencies.
4) No base_nacl_nonsfi is needed only when
"disable_nacl == 0 and disable_nacl_untrusted == 0". So we can merge
the targets.

BUG=358465
TEST=Ran trybot.

Review URL: https://codereview.chromium.org/672213002

Cr-Commit-Position: refs/heads/master@{#300933}

base/base_nacl.gyp

@@ -36,7 +36,7 @@
             ],
           },
           'dependencies': [
-            '<(DEPTH)/native_client/tools.gyp:prep_toolchain',
+            '../native_client/tools.gyp:prep_toolchain',
           ],
         },
         {
@@ -59,22 +59,15 @@
             ],
           },
           'dependencies': [
-            '<(DEPTH)/third_party/icu/icu_nacl.gyp:icudata_nacl',
-            '<(DEPTH)/third_party/icu/icu_nacl.gyp:icui18n_nacl',
-            '<(DEPTH)/third_party/icu/icu_nacl.gyp:icuuc_nacl',
-            '<(DEPTH)/native_client/tools.gyp:prep_toolchain',
+            '../native_client/tools.gyp:prep_toolchain',
+            '../third_party/icu/icu_nacl.gyp:icudata_nacl',
+            '../third_party/icu/icu_nacl.gyp:icui18n_nacl',
+            '../third_party/icu/icu_nacl.gyp:icuuc_nacl',
           ],
         },
-      ],
-    }],
-    ['disable_nacl==0', {
-      'targets': [
         {
           'target_name': 'base_nacl_nonsfi',
           'type': 'none',
-          'include_dirs': [
-            '<(DEPTH)/native_client/src/public/linux_syscalls',
-          ],
           'variables': {
             'base_target': 1,
             'nacl_untrusted_build': 1,
@@ -116,8 +109,8 @@
             'rand_util_nacl.cc',
           ],
           'dependencies': [
-            '<(DEPTH)/native_client/tools.gyp:prep_toolchain',
-            '<(DEPTH)/third_party/libevent/libevent_nacl_nonsfi.gyp:event_nacl_nonsfi',
+            '../native_client/tools.gyp:prep_toolchain',
+            '../third_party/libevent/libevent_nacl_nonsfi.gyp:event_nacl_nonsfi',
           ],
         },
       ],