Fix is_link_cmd command to support response file

[ryanking13]

Fix pyodide/pyodide#5131

This fixes the is_link_cmd function which is used to detect the linker invocation.

If the command is too long, build systems like Ninja (or CMake, etc) use a response file to store the commands into a file. For instance, the command

emcc.py -o output.so input1.o input2.o ... inputN.o

becomes

emcc.py @output.so.rsp

where the file output.so.rsp stores all the commandline parameters.

Therefore, this PR fixes the is_link_cmd to detect the response file.

Note that I also removed the usage of re module, as I found that using string commands are much cheaper than compiling the regex.

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