TBR: i#1801 clang build x86 test failure: add CLANG macro

Commit log for first patchset:
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i#1801 clang build x86 test failure: add CLANG macro

- add CLANG macron for clang build
- use different stack alignment in asm_defines.asm with 32-bit clang build
- fixed linux.signalfd on 32-bit clang build
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[zhaoqin, 2015-10-28 15:58:51]

On 2015/10/28 15:58:10, zhaoqin wrote:

It is not a TBR, use -t by mistake.

[bruening, 2015-10-28 17:31:04]

On 2015/10/28 15:58:10, zhaoqin wrote:
> - add CLANG macron for clang build
"macron"?

> - use different stack alignment in asm_defines.asm with 32-bit clang build
> - fixed linux.signalfd on 32-bit clang build

Inconsistent tense: "add, use, fixed"

[zhaoqin, 2015-10-28 18:29:43]

Commit log for latest patchset:
---------------
i#1801 clang build x86 test failure: add CLANG macro

- add CLANG macro for clang build
- use different stack alignment in asm_defines.asm with 32-bit clang build

Review-URL: https://codereview.appspot.com/273110043
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[bruening, 2015-10-28 18:41:54]

LGTM

https://codereview.appspot.com/273110043/diff/1/core/lib/genapi.pl
File core/lib/genapi.pl (right):

https://codereview.appspot.com/273110043/diff/1/core/lib/genapi.pl#newcode263
core/lib/genapi.pl:263: $def eq "MACOS" || $def eq "X64" || $def eq "CLANG" ||
This implies that we would make a separate package build for clang?  Would our
headers differ?  Though I guess not listing it here implies the headers would
look different for packages built w/ clang or w/o.

[zhaoqin, 2015-10-28 19:06:23]

https://codereview.appspot.com/273110043/diff/1/core/lib/genapi.pl
File core/lib/genapi.pl (right):

https://codereview.appspot.com/273110043/diff/1/core/lib/genapi.pl#newcode263
core/lib/genapi.pl:263: $def eq "MACOS" || $def eq "X64" || $def eq "CLANG" ||
On 2015/10/28 18:41:54, bruening wrote:
> This implies that we would make a separate package build for clang?  Would our
> headers differ?  Though I guess not listing it here implies the headers would
> look different for packages built w/ clang or w/o.

It looks like we can remove it, it does not really affect the generated api
headers. I only added it here to match MACOS, basically any where MACOS is
added, CLANG is added.

CLANG only affects cpp2asm_defines.h and DynamoRIOConfig.cmake, the stack
alignment adjustment is exposed in cpp2asm_defines.h.

[zhaoqin, 2015-10-28 19:28:21]

Committed as
https://github.com/DynamoRIO/dynamorio/commit/8cce9cf0e7b1a3493b34503b80499c8...

Final commit log: 
---------------
i#1801 clang build x86 test failure: add CLANG macro

- add CLANG macro for clang build
- use different stack alignment in asm_defines.asm with 32-bit clang build

Review-URL: https://codereview.appspot.com/273110043
---------------