Disable "-fipa-sra" when using "--enable-debuginfo"

Disable "-fipa-sra" when using "--enable-debuginfo"

To better enable dynamic tracing tools (e.g. "bpftrace") this change
disables the "-fipa-sra" compilation optimization. This way, function
signatures are not changed by the compiler, which allows us to better
attach to kprobes and kretprobes with dynamic tracing tools. Otherwise,
the compiler may append ".isra" to the function name, and possibly
change the function arguments as well.

Reviewed-by: Matt Ahrens <matt@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Igor Kozhukhov <igor@dilos.org>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Prakash Surya <prakash.surya@delphix.com>
Closes #9921