BUG: Disable aligned attribute to fix Apple GCC 4.2.1 seg fault

Commit 2f96c578 fixed the configure test checking if aligned
attributes were supported by the compiler. Then commit e906441e
disabled the test for Gcc 4.1 to prevent a similar error.

This commit ensures that the configure test also excludes Apple
Gcc 4.2.1 (without llvm support) by forcing the configure test to
be in "Debug" mode.

When this issue was first encountered by Brad, the problem was occurring
in Debug mode and he narrowed it down to the block of code in the try_compile
and tried to use it as a detector. Slicer appears to have encountered the
same issue in release mode, but the bug detector only detects it in Debug
mode.

Fixes #3172 - See https://itk.icts.uiowa.edu/jira/browse/ITK-3172

Co-authored-by: Bradley Lowekamp <blowekamp@mail.nih.gov>

Change-Id: I67c870d8f68b0fd2fafaf470738bf125887165d7
Merge branch 'ITK-3172-unsupported-aligned-attribute-gcc421' into release

Change-Id: Ibf85f508674555692521f7efabb38b406f2cb56d