How to determine which compiler is currently being used from within a build file

Right now, specific compilation flags can't be enabled/disabled depending on the compiler:
```xml

```

(If this isn't actually true, this issue can be ignored. Documentation just needs to be added.)

It seems like the `isMsvc` variable is available to check when using MSVC. Perhaps standard variables in the same vein may be helpful: `isGcc`, `isClang`, etc.

```xml

```

Or perhaps a more general solution:

```xml

```

Otherwise, it may be useful to set a define in each toolchain that specifies which compiler has been chosen.

```xml

```

```xml

```