Clang path resolution

[XuJiandong]

Running cd contracts/project1 && make build does not work due to the following issue:

cur_dir = $(dir $(abspath $(firstword $(MAKEFILE_LIST))))

CLANG := $(shell $(TOP)/scripts/find_clang)

This Makefile setup assumes that make is invoked from the workspace root, which breaks relative path resolution when run from a subdirectory.

[XuJiandong]

One suggestion:

cur_dir = $(dir $(abspath $(lastword $(MAKEFILE_LIST))))
CLANG := $(shell $(TOP)/../../scripts/find_clang)

[xxuejie]

It's actually quite hard to say that $(TOP)/../../scripts/find_clang will definitely work, what if someone just uses contracts/v1/foo as the path for a CKB script?

So the original idea is that if you cd contracts/project1, you are expected to use make build TOP=$(pwd)/../.., in other words, manually providing TOP as a parameter.

The originally design works that you can also do make build CONTRACT=project1 to build a single contract.

If we really want a child contract to infer the correct value for TOP, maybe a better design is to traverse all upper-level directories, until we can find a folder containing .git or scripts/find_clang. That will be a much better design.