Wrong path for clang-scan-deps

[TroyKomodo]

rules_cc/cc/private/toolchain/unix_cc_configure.bzl

Lines 451 to 456 in 34f61b4

	deps_scanner = "cpp-module-deps-scanner_not_found"
	if is_clang:
	cc_str = str(cc)
	path_arr = cc_str.split("/")[:-1]
	path_arr.append("clang-scan-deps")
	deps_scanner = "/".join(path_arr)

We should not be using a assumed hard coded path to find clang-scan-deps and should rather find it via path.

[fmeum]

It seems reasonable to prefer the sibling to CC if it exists, but a fall back to searching on the path wouldn't hurt.