Fix various tests to use -no-pie linker flag when needed

Fix various tests to use -no-pie linker flag when needed

Various tests use test code written in i386 / x86_64 assembly that cannot
be used to create PIE executables. Therefore compilation of test programs
failed on systems where the compiler default is to create PIE executable.

The solution is to use -no-pie linker flag, however, such flag may not
(is not) supported by all compilers GDB needs to support (e.g. gcc 4.8).
To handle this, introduce a new flag to gdb_compile - nopie - which
inserts -no-pie linker flag where supported and is no-op where it is
not. By default, -no-pie flag is inserted since most modern compiler do
support it.