SassTask doesn't always show downstream errors (was SassCompiler ignores `style`)

[elt4n0]

Description
When the SassTask implements an instance of SassCompiler to execute instead of ScssPhpCompiler the style property passed is ignored.

Steps To Reproduce
Run a buildfile with a SassTask that contains a style property where SassTask::getExecutable() returns a non-null value. (e. g. when sass is installed globally using npm).

Expected behavior
The style parameter should be passed to whichever tool is being used to compile Sass.

[mrook]

Hi, style is actually passed on, but errors (when style is not a value that sass recognizes) are not returned correctly. Commit 7cee2b3 fixes this.

For example,

<sass style="compact" outputpath="." useSass="true" failOnError="true">
    <fileset dir="."/>
</sass>

now results in

BUILD FAILED
phing-tests/1863/build.xml:3:71 Sass exited with return code 64 and message '"compact" is not an allowed value for option "--style".'