Function get_backtrace_style

Checks whether the standard library's panic hook will capture and print a backtrace.

This function will, if a backtrace style has not been set via set_backtrace_style, read the environment variable RUST_BACKTRACE to determine a default value for the backtrace formatting:

The first call to get_backtrace_style may read the RUST_BACKTRACE environment variable if set_backtrace_style has not been called to override the default value. After a call to set_backtrace_style or get_backtrace_style, any changes to RUST_BACKTRACE will have no effect.

RUST_BACKTRACE is read according to these rules:

• 0 for BacktraceStyle::Off
• full for BacktraceStyle::Full
• 1 for BacktraceStyle::Short
• Other values are currently BacktraceStyle::Short, but this may change in the future

Returns None if backtraces aren't currently supported.