Moved clang flags out of the root build.gardle.

Collected clang args in ClangArgs.kt
Switched dependencies/build.gradle to KonanTarget.
Introduced KonanProperties to take care of target specific properties.

runtime/build.gradle

@@ -25,7 +25,6 @@ targetList.each { targetName ->
         dependsOn ":common:${targetName}Hash"
         dependsOn "${targetName}Launcher"
         target targetName
-        compilerArgs targetArgs[targetName]
         compilerArgs '-g'
         compilerArgs '-I' + project.file('../common/src/hash/headers')
         compilerArgs '-I' + project.file(rootProject.ext.get("${targetName}LibffiDir") + "/include")
@@ -38,14 +37,13 @@ targetList.each { targetName ->
         name "launcher"
         srcRoot file('src/launcher')
         target targetName
-        compilerArgs targetArgs[targetName]
         compilerArgs '-g'
         compilerArgs '-I' + project.file('../common/src/hash/headers')
         compilerArgs '-I' + project.file('src/main/cpp')
     }
 }
 
-task hostRuntime(dependsOn: "${rootProject.ext.host}Runtime")
+task hostRuntime(dependsOn: "${hostName}Runtime")
 
 task clean {
     doLast {