gstlal: add raspberry pi support

- following input from Steffen

gstlal/configure.ac

@@ -265,10 +265,13 @@ AC_SUBST([PYGOBJECT_LIBS])
 
 # on Debian the file is /usr/lib/x86_64-linux-gnu/libpython2.7.so
 # on SL7 the file is /usr/lib64/libpython2.7.so
+# on raspberry pi the file is /usr/lib/aarch64-linux-gnu/libpython2.7.so
 AC_SUBST([PYTHON_ABI_FLAGS], [])
 AC_SUBST([PYTHON_LIB_SUFFIX], [so])
 if test -a "/usr/lib/x86_64-linux-gnu/libpython2.7.so" ; then
 	AC_SUBST([PYTHON_LIB_LOC], [/usr/lib/x86_64-linux-gnu])
+elif test -a "/usr/lib/aarch64-linux-gnu/libpython2.7.so" ; then
+	AC_SUBST([PYTHON_LIB_LOC], [/usr/lib/aarch64-linux-gnu])
 elif test -a "/usr/lib64/libpython2.7.so" ; then
 	AC_SUBST([PYTHON_LIB_LOC], [/usr/lib64])
 elif test -a "/opt/local/lib/libpython2.7.dylib" ; then