Makefile: simplify fuchsia Go build
Makefile: simplify fuchsia Go build

$(SOURCEDIR)/scripts/devshell/go seems to work out of the box.

google/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller