Why is stdlib required to link programs? [duplicate]

This question already has an answer here:

• What is the use of _start() in C? 2 answers

Take the following C program:

int main(){}

It's not using anything from the C standard library.
I assumed we could disable linkage through -nostdlib.

However, this results in the following error:

$ gcc -nostdlib -o main main.c
/usr/bin/ld: warning: cannot find entry symbol _start; defaulting to 0000000000400150

Can someone clarify what the _start symbol is and who is responsible for providing it?
How would one go about using -nostdlib?

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Per the docs, I have also tried:

$ gcc -nostdlib -o main main.c -lgcc

Same behaviour is seen with clang.