Multiple packages: use target-g++ instead of target-c++ as CXX

It is more explicit and conforms with other packages.

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
libgdamm: add update macro

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
icu4c: symlink <lib>53.dll.a to <lib>.dll.a

Fixes #454.

Signed-off-by: Timothy Gu <timothygu99@gmail.com>