https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66029
--- Comment #11 from JD <t at sharklasers dot com> ---
Yes, it's non-empty:
$ ar --help | grep plugin
Usage: ar [emulation options] [-]{dmpqrstx}[abcDfilMNoPsSTuvV] [--plugin
<name>] [member-name] [count] archive-file file...
--plugin <p> - load the specified plugin
ar: supported targets: elf64-x86-64 elf32-i386 elf32-x86-64 a.out-i386-linux
pei-i386 pei-x86-64 elf64-l1om elf64-k1om elf64-little elf64-big elf32-little
elf32-big plugin srec symbolsrec verilog tekhex binary ihex
$ echo "int main () {}" | gcc -x c++ -O2 - -flto -v 2>&1 | grep "collect2
-plugin"
gcc5.1/lib/gcc/x86_64-unknown-linux-gnu/5.1.0/collect2 -plugin
gcc5.1/lib/gcc/x86_64-unknown-linux-gnu/5.1.0/liblto_plugin.so
-plugin-opt=gcc5.1/lib/gcc/x86_64-unknown-linux-gnu/5.1.0/lto-wrapper
-plugin-opt=-fresolution=/tmp/ccuU0Nuu.res -plugin-opt=-pass-through=-lgcc
-plugin-opt=-pass-through=-lgcc_s -plugin-opt=-pass-through=-lc
-plugin-opt=-pass-through=-lgcc -plugin-opt=-pass-through=-lgcc_s -flto
--eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2
/usr/lib/../lib64/crt1.o /usr/lib/../lib64/crti.o
gcc5.1/lib64/gcc/x86_64-unknown-linux-gnu/5.1.0/crtbegin.o
-Lgcc5.1/lib64/gcc/x86_64-unknown-linux-gnu/5.1.0
-Lgcc5.1/lib64/gcc/x86_64-unknown-linux-gnu/5.1.0/../../../../lib64
-L/lib/../lib64 -L/usr/lib/../lib64
-Lgcc5.1/lib64/gcc/x86_64-unknown-linux-gnu/5.1.0/../../.. /tmp/ccUoazVJ.o
-lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s
--no-as-needed gcc5.1/lib64/gcc/x86_64-unknown-linux-gnu/5.1.0/crtend.o
/usr/lib/../lib64/crtn.o
