a) if the sample should only be built if "wxUSE_FOO" is enabled, locate
the test for "wxUSE_FOO = yes" in configure.in and add a line
SAMPLES_SUBDIRS="$SAMPLES_SUBDIRS foo" under it
b) if it should be always built, locate the line "if test $wxUSE_GUI = yes"
near the end of configure.in and modify the assignment to
SAMPLES_SUBDIRS to include "foo" (put in alphabetical order)
a) if the sample should only be built if "wxUSE_FOO" is enabled, locate
the test for "wxUSE_FOO = yes" in configure.in and add a line
SAMPLES_SUBDIRS="$SAMPLES_SUBDIRS foo" under it
b) if it should be always built, locate the line "if test $wxUSE_GUI = yes"
near the end of configure.in and modify the assignment to
SAMPLES_SUBDIRS to include "foo" (put in alphabetical order)