Fix a broken dependency in generate_pnacl_support_extension

Fix a broken dependency in generate_pnacl_support_extension

the '*_eh_a' outputs doesn't seem to be generated anymore, because of this you get the following log if you compile the pnacl_support_extension target twice:

[master]E:\src\chrome\src>ninja -C out\Release pnacl_support_extension -d explain
ninja: Entering directory `out\Release'
ninja explain: output pnacl/pnacl_public_x86_32_libgcc_eh_a doesn't exist
ninja explain: pnacl/pnacl_public_pnacl_json is dirty
ninja explain: pnacl/pnacl_public_x86_32_crtbegin_o is dirty
ninja explain: pnacl/pnacl_public_x86_32_ld_nexe is dirty
ninja explain: pnacl/pnacl_public_x86_32_libcrt_platform_a is dirty
ninja explain: pnacl/pnacl_public_x86_32_libgcc_a is dirty
ninja explain: pnacl/pnacl_public_x86_32_libgcc_eh_a is dirty
ninja explain: pnacl/pnacl_public_x86_32_libpnacl_irt_shim_a is dirty
ninja explain: pnacl/pnacl_public_x86_32_pnacl_llc_nexe is dirty
ninja explain: pnacl/pnacl_public_x86_64_crtbegin_o is dirty
ninja explain: pnacl/pnacl_public_x86_64_ld_nexe is dirty
ninja explain: pnacl/pnacl_public_x86_64_libcrt_platform_a is dirty
ninja explain: pnacl/pnacl_public_x86_64_libgcc_a is dirty
ninja explain: pnacl/pnacl_public_x86_64_libgcc_eh_a is dirty
ninja explain: pnacl/pnacl_public_x86_64_libpnacl_irt_shim_a is dirty
ninja explain: pnacl/pnacl_public_x86_64_pnacl_llc_nexe is dirty
ninja explain: obj/ppapi/native_client/src/untrusted/pnacl_support_extension/pnacl_support_extension.actions_rules_copies.stamp is dirty
[2/2] STAMP obj\ppapi\native_client\src\untrusted\pnacl_support_extension\pnacl_support_extension.actions_rules_copies.stamp

BUG=439228
Committed: https://crrev.com/ed4c0454e327c0806f0102ef8edd4700eebf843e
Cr-Commit-Position: refs/heads/master@{#312891}

[Sébastien Marchand, 2015-01-23 18:14:47]

sebmarchand@chromium.org changed reviewers:
+ bradnelson@chromium.org

[Sébastien Marchand, 2015-01-23 18:14:48]

PTAL.

[bradn, 2015-01-23 18:20:15]

bradnelson@google.com changed reviewers:
+ bradnelson@google.com

[bradn, 2015-01-23 18:20:15]

lgtm

[bradn, 2015-01-23 18:20:28]

The CQ bit was checked by bradnelson@google.com

[commit-bot: I haz the power, 2015-01-23 18:21:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/873773002/1

[commit-bot: I haz the power, 2015-01-23 18:30:16]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-01-23 18:30:17]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[bradnelson, 2015-01-23 18:32:25]

lgtm

[bradn, 2015-01-23 18:32:29]

The CQ bit was checked by bradnelson@google.com

[commit-bot: I haz the power, 2015-01-23 18:33:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/873773002/1

[commit-bot: I haz the power, 2015-01-23 18:34:56]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-01-23 18:34:57]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[bradn, 2015-01-23 18:45:44]

The CQ bit was checked by bradnelson@google.com

[commit-bot: I haz the power, 2015-01-23 18:47:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/873773002/1

[commit-bot: I haz the power, 2015-01-23 19:17:03]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-23 19:18:03]

Patchset 1 (id:??) landed as
https://crrev.com/ed4c0454e327c0806f0102ef8edd4700eebf843e
Cr-Commit-Position: refs/heads/master@{#312891}