Remove ability to select RADSAN_ERROR_MODE default to "exit"

[cjappl]

This in my testing fixes

realtime-sanitizer/rtsan#25

The main crux of it was removing any C++ standard library from radsan, including things like std::cin, std::cout and std::function. These were all concentrated around the area of being able to select the start/stop/continue error modes.

I'm putting this up for draft so we can discuss. We could consider moving to the more traditional sanitizer options, which presumably have a work around for this.

From this build, regular c files with interceptors work well from inside the docker container:

root@5520df3206e2:/my_repo# cat blah.c
#include <stdlib.h>

[[clang::realtime]]
int main(void)
{
    int *p = malloc(10 * sizeof(int));
    (void)p;
    return 0;
}
root@5520df3206e2:/my_repo# clang -fsanitize=realtime blah.c
root@5520df3206e2:/my_repo# ./a.out
Real-time violation: intercepted call to real-time unsafe function `malloc` in real-time context! Stack trace:
    #0 0xaaaaca775f78 in radsan::printStackTrace() /llvm-project/compiler-rt/lib/radsan/radsan_stack.cpp:44:3
    #1 0xaaaaca775dd4 in radsan::Context::expectNotRealtime(char const*) /llvm-project/compiler-rt/lib/radsan/radsan_context.cpp:46:5
    #2 0xaaaaca77681c in expectNotRealtime /llvm-project/compiler-rt/lib/radsan/radsan_interceptors.cpp:39:29
    #3 0xaaaaca77681c in malloc /llvm-project/compiler-rt/lib/radsan/radsan_interceptors.cpp:247:3
    #4 0xaaaaca799adc in main (/my_repo/a.out+0x29adc)
    #5 0xffffa3d373f8  (/lib/aarch64-linux-gnu/libc.so.6+0x273f8) (BuildId: 3ba44e06b9dc66aeeb2651db4dd015ffaf6e0849)
    #6 0xffffa3d374c8 in __libc_start_main (/lib/aarch64-linux-gnu/libc.so.6+0x274c8) (BuildId: 3ba44e06b9dc66aeeb2651db4dd015ffaf6e0849)
    #7 0xaaaaca775c2c in _start (/my_repo/a.out+0x5c2c)

root@5520df3206e2:/my_repo#

And our original problem is fixed:

root@5520df3206e2:/my_repo# echo 'int main() { return 0; }' | clang -fsanitize=realtime -x c - -o /dev/null
root@5520df3206e2:/my_repo#

[cjappl]

We now just die without any option to do anything otherwise. This is a loss of functionality in favor of getting C back up and running. I also think this is the most reasonable default of the modes we have right now

[cjappl]

This function with std::function, cout, cin, noskipws was the main culprit of problems relating to the C++ standard library

[cjappl]

It goes without saying this test is now not doing much

[cjappl]

Closing, we are simplifying this in our upstreaming branch for now