Skip AsanTestCase and AsanTestReportDataCase on Darwin

Skip AsanTestCase and AsanTestReportDataCase on Darwin

Summary:
This patch skips tests which cause the following error:
```
1: test_with_dsym (TestMemoryHistory.AsanTestCase) ...
os command: make clean ; make MAKE_DSYM=YES ARCH=x86_64 CC="/Users/IliaK/p/llvm/build_ninja/bin/clang"
with pid: 9475
stdout: rm -f "a.out"  main.o main.d main.d.tmp
rm -f -r "a.out.dSYM"
/Users/IliaK/p/llvm/build_ninja/bin/clang  -fsanitize=address -fsanitize-address-field-padding=1 -g -arch x86_64   -I/Users/IliaK/p/llvm/tools/lldb/test/make/../../include   -c -o main.o main.c
/Users/IliaK/p/llvm/build_ninja/bin/clang  main.o  -fsanitize=address -fsanitize-address-field-padding=1 -g -arch x86_64   -I/Users/IliaK/p/llvm/tools/lldb/test/make/../../include   -o "a.out"

stderr: clang: error: unknown argument: '-fsanitize-address-field-padding=1'
clang: error: unsupported argument 'address' to option 'fsanitize='
ld: file not found: /Users/IliaK/p/llvm/build_ninja/bin/../lib/clang/3.7.0/lib/darwin/libclang_rt.asan_osx_dynamic.dylib
clang-3.7: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [a.out] Error 1

retcode: 2

ERROR

os command: make clean
with pid: 9521
stdout: rm -f "a.out"  main.o main.d main.d.tmp
rm -f -r "a.out.dSYM"

stderr:
retcode: 0

Restore dir to: /Users/IliaK/p/llvm/tools/lldb

======================================================================
ERROR: test_with_dsym (TestMemoryHistory.AsanTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/IliaK/p/llvm/tools/lldb/test/lldbtest.py", line 612, in wrapper
    func(*args, **kwargs)
  File "/Users/IliaK/p/llvm/tools/lldb/test/lldbtest.py", line 456, in wrapper
    return func(self, *args, **kwargs)
  File "/Users/IliaK/p/llvm/tools/lldb/test/functionalities/asan/TestMemoryHistory.py", line 24, in test_with_dsym
    self.buildDsym (None, compiler)
  File "/Users/IliaK/p/llvm/tools/lldb/test/lldbtest.py", line 1496, in buildDsym
    if not module.buildDsym(self, architecture, compiler, dictionary, clean):
  File "/Users/IliaK/p/llvm/tools/lldb/test/plugins/builder_darwin.py", line 16, in buildDsym
    lldbtest.system(commands, sender=sender)
  File "/Users/IliaK/p/llvm/tools/lldb/test/lldbtest.py", line 370, in system
    raise CalledProcessError(retcode, cmd)
CalledProcessError: Command 'make clean ; make MAKE_DSYM=YES ARCH=x86_64 CC="/Users/IliaK/p/llvm/build_ninja/bin/clang" ' returned non-zero exit status 2
Config=x86_64-clang
----------------------------------------------------------------------
```

Also this patch fixes findBuiltClang() by looking a clang in the build folder.

BTW, another patch was made in October 2014, but it wasn't committed: http://reviews.llvm.org/D6272.

Reviewers: abidh, zturner, emaste, jingham, jasonmolenda, granata.enrico, DougSnyder, clayborg

Reviewed By: clayborg

Subscribers: lldb-commits, DougSnyder, granata.enrico, jasonmolenda, jingham, emaste, zturner, abidh, clayborg

Differential Revision: http://reviews.llvm.org/D7958

llvm-svn: 232016