adjust building from source without LLVM process

The idea here is that the zig2 executable is perhaps the more useful
deliverable until we implement our own optimization passes. This will
allow system packages to provide Zig, and use it to compile Zig
projects, all without LLVM!

bootstrap.c

@@ -42,11 +42,6 @@ static void run(char **argv) {
     if (WEXITSTATUS(status) != 0)
         panic("child process failed");
 }
-
-static void run_execv(char **argv) {
-    if (execv(argv[0], argv) == -1 && errno == ENOENT) return;
-    perror("execv failed");
-}
 #endif
 
 static void print_and_run(const char **argv) {
@@ -87,9 +82,6 @@ static const char *get_host_triple(void) {
 }
 
 int main(int argc, char **argv) {
-    argv[0] = "./zig2";
-    run_execv(argv);
-
     const char *cc = get_c_compiler();
     const char *host_triple = get_host_triple();
 
@@ -188,7 +180,4 @@ int main(int argc, char **argv) {
         };
         print_and_run(child_argv);
     }
-
-    run_execv(argv);
-    panic("build script failed to create valid zig2 executable");
 }