https://bugzilla.mozilla.org/show_bug.cgi?id=1076892
http://openwall.com/lists/oss-security/2014/12/05/21

this is preventing firefox from shipping an ASLR-compatible position-independent executable.

You can test this with the following code:

-----test.c-----
#include <unistd.h>
int main() {
 execl("/usr/bin/xmessage", "xmessage", "test", NULL);
}
-----test.c-----

built this way:

 gcc -o test-pie -pie -fPIC test.c
 gcc -o test-nonpie test.c

you'll be able to launch both ./test-pie and ./test-nonpie from the command line (an xmessage window should pop up), but double-clicking test-pie in nautilus yields:

 Could not display "test-pie".
 There is no application installed for "shared library" files.

fwiw, /usr/bin/file reports test-pie as an "LSB shared object", and test-nonpie as an "LSB executable".