Run ifchange with shell explicitly, workaround of noexec mount

configure.ac

@@ -4144,7 +4144,7 @@ guard=INCLUDE_RUBY_CONFIG_H
 } | tr -d '\015' |
 (
   AS_IF([test "x$CONFIGURE_TTY" = xyes], [color=--color], [color=])
-  exec ${tooldir}/ifchange $color "${config_h}" -
+  exec ${SHELL} ${tooldir}/ifchange $color "${config_h}" -
 ) >&AS_MESSAGE_FD || AC_MSG_ERROR([failed to create ${config_h}])
 tr -d '\015' < largefile.h > confdefs.h
 rm largefile.h

template/Makefile.in

@@ -217,7 +217,7 @@ ARFLAGS       = @ARFLAGS@$(empty)
 RANLIB        = @RANLIB@
 AS            = @AS@
 ASFLAGS       = @ASFLAGS@ $(ARCH_FLAG) $(INCFLAGS)
-IFCHANGE      = $(tooldir)/ifchange
+IFCHANGE      = $(SHELL) $(tooldir)/ifchange
 OBJDUMP       = @OBJDUMP@
 OBJCOPY       = @OBJCOPY@
 HAVE_GIT      = @HAVE_GIT@