fix(build): fix incorrectly-escaped armlink preprocessor definitions

Preprocessor definitions that are passed to armlink are currently not
correctly escaped, resulting in the shell trying to parse the
parentheses contained in some of the preprocessor definitions:

```
  LD      build/tegra/t210/release/bl31/bl31.elf
/bin/sh: 1: Syntax error: "(" unexpected
```

This change ensures that these preprocessor definitions are adequately
escaped for the shell.

Change-Id: I9d2c60fa60c0aa00770417a68f900e9fb84b4669
Signed-off-by: Chris Kay <chris.kay@arm.com>
1 file changed