its value is derived from three sources:
the defaults for the Go toolchain used to build the program,
amended to match the Go version listed in `go.mod`,
and then overridden by explicit `//go:debug` lines in the program.

The [GODEBUG History](#history) gives the exact defaults for each Go toolchain version.
For example, Go 1.21 introduces the `panicnil` setting,
controlling whether `panic(nil)` is allowed;

use. You can do this by setting the generic CC_FOR_TARGET or the
more specific CC_FOR_${GOOS}_${GOARCH} (for example, CC_FOR_linux_arm)
environment variable when building the toolchain using make.bash,
or you can set the CC environment variable any time you run the go tool.

The CXX_FOR_TARGET, CXX_FOR_${GOOS}_${GOARCH}, and CXX
environment variables work in a similar way for C++ code.

and instruction selection occurs partly after code generation.
The assembler works on the semi-abstract form, so
when you see an instruction like <code>MOV</code>
what the toolchain actually generates for that operation might
not be a move instruction at all, perhaps a clear or load.
Or it might correspond exactly to the machine instruction with that name.

			// of treating these fields as the USTAR prefix field.
			//
			// Note that this will not use the fallback logic for all possible
			// files generated by a pre-Go1.8 toolchain. If the generated file
			// happened to have a prefix field that parses as valid
			// atime and ctime fields (e.g., when they are valid octal strings),
			// then it is impossible to distinguish between a valid GNU file

// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// This program can be used as go_ios_$GOARCH_exec by the Go tool.
// It executes binaries on an iOS device using the XCode toolchain
// and the ios-deploy program: https://github.com/phonegap/ios-deploy
//
// This script supports an extra flag, -lldb, that pauses execution
// just before the main program begins and allows the user to control