[cmake] ENABLE_MULTIARCH option

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[cutes] Qt 5.1(0)/5.2: conditional compilation

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
generalize env functions

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
v8 support: move file tree to v8 subdirs

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[cutes] implementation suitable for any js engine

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>