Revert "build c2str.exe with the host compiler; default it to gcc if cross prefix given"

This reverts commit 41fa74fc8485be8e7f6eb92de93997d8e3b0a7f7. Reasons for the revert: 1. The commit message is lacking and the use case is not obvious. At the very least a concrete example of use case should be given (likely cross-building tcc on platform X for running on platform Y), followed by an issue description in such use case, and fix descr. (e.g. "On platform X, when running ./configure ... && make ..., the build fails because whatever. this commit does Y and fixes it"). 2. assign_opt is used incorrectly: 1st arg must be --OPTNAME=VALUE but it's not. The only thing it does is unconditional host_cc=gcc if --cross-prefix=... is used - no need for "assign_opt" at all. 3. cross-building tcc currently has several triggers: build/target cpu differ, or build/target OS differ, or --cross-prefix=... is used, but that commit only covers the --cross-prefix=... case. It's possible that it's intentional to only cover one case, but if so then it's not explained why. 4. The var name host_cc is likely incorrect and probably meant to be "native_cc", judging by the assigned value "gcc". 5. "gcc" is used unconditionally in such case, without any way to use a different native compiler (assuming that's indeed the goal). A better approach is likely supporting --native-cc=... option which defaults to $cc (which already defaults to "gcc") _before_ $cross_prefix is added in-front.

AHAvi Halachmi (:avih) committed 10 months ago