[SYCLomatic][intercept-build] Fix lit tests related to intercept-build run failed in the env that toolchain is not available from environment variable `PATH`

[tomflinda]

The related cases are as follows:

1. dpct/cmp-cmds-linker-entry-src-files/one.cu
2. dpct/dpct-intercept-build/main.cpp
3. dpct/gen_build_script2/hello.cu
4. dpct/gen_build_script3/hello.cu

Signed-off-by: chenwei.sun [email protected]