MFH: r469589

stage-qa: Change stripped check to only look for .debug_info.

'strip -x', and splitting out debug symbols with objcopy, will leave
a .symtab section but will still remove the .debug_info section. file(1)
shows this distinction as well after the use of 'strip -x':

work/tcl8.7a1/unix/libtcl8.7.so:       ELF 64-bit LSB shared object, x86-64, version 1 (FreeBSD), dynamically linked, with debug_info, not stripped
work/stage/usr/local/lib/libtcl8.7.so: ELF 64-bit LSB shared object, x86-64, version 1 (FreeBSD), dynamically linked, not stripped

This fixes false-positives when using install-strip and symbol splitting.

With hat: portmgr

Approved by: portmgr (implicit)