install: shell parameter expansions can be used in directory names Fixes automake bug#11232. GNU automake used to support shell parameter expansion and command substitutions in installation directories, but that was inadvertently broken by commit v1.11-759-g368f1c4 "install: don't create empty dirs when an empty 'foo_PRIMARY' is used" of 18-03-2012, where shell quoting of generated MKDIR_P command was changed from double to single quotes in 3 places, while some 21 other places still use double quotes for generated MKDIR_P commands. * lib/am/data.am: Use double quotes for generated "mkdir -p" commands. * lib/am/libs.am: Likewise. * lib/am/ltlib.am: Likewise. Signed-off-by: Dmitry V. Levin <ldv@altlinux.org> Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>