avr-gcc-ar fails to run

[Mikko Rantanen]

Fresh raspbian lite (April 2017) with apt-get install gcc-avr (1:4.8.1+Atmel3.4.4-2).

```
pi@raspberrypi:~ $ avr-gcc-ar --help
avr-gcc-ar: Cannot find plugin 'liblto_plugin.so'
```

Based on strace, avr-gcc-ar finds the liblto_plugin.so but doesn't recognize it as it doesn't have execute access. Giving execute access to the library (which is behind a symlink) provides the following problem:

```
pi@raspberrypi:~ $ sudo chmod a+x /usr/lib/gcc/avr/4.8.1/liblto_plugin.so.0.0.0
pi@raspberrypi:~ $ avr-gcc-ar --help
sorry - this program has been built without plugin support
```

avr-gcc-ar attempts to execute avr-ar, which doesn't support the --plugin option.

Might be an upstream bug, but I don't have a pure raspbian jessie installation to test this with.

gcc works around the first issue by specifically passing R_OK to the find_a_file function responsible for locating the liblto. This was changed in 2013: https://github.com/gcc-mirror/gcc/commit/0dc1ebca5751c076a9ea07a7e6d6e8428bdbe73b - unfortunately this fix has gone in after 4.8.1 release based on the timestamps.

The second issue feels more a problem of the binutils/gcc compatibility in raspbian/jessie.

System: Linux raspberrypi 4.4.50+ #970 Mon Feb 20 19:12:50 GMT 2017 armv6l GNU/Linux
Libc package: 2.19-18+deb8u7