math/py-numpy: Fix static library check that assumes atlas is installed

- Use BUILD_DEPENDS to check for the atlas static library at pre-build
  time instead of checking if the file exists (False if atlas is not
  installed)

- Replace IGNORE with a message to the user notifying them that
  an atlas install WITH_STATIC is needed, and provide clues as possible
  actions without being too prescriptive.

As discussed with eadler@, a correct resolution to "ports depending on other ports with specific OPTIONS" is either an atlas slave port
(ie: atlas-static), or to modify atlas to install both shared and static
libraries.

This change is a net gain on the existing broken behaviour, by fixing
the check, while retaining the user notification.

PR:		ports/178094
Reviewed by:	jhibbits, eadler
Approved by:	maintainer timeout (7+ months)

math/py-numpy/Makefile

@@ -56,9 +56,14 @@ DISTFILES+=	${FP_ARCH}/fenv.c?p=203441:fp ${FP_ARCH}/fenv.h?p=203441:fp
 
 .if ${PORT_OPTIONS:MATLAS}
 LIB_DEPENDS+=	atlas.2:${PORTSDIR}/math/atlas
-.if !exists(${LOCALBASE}/lib/libalapack.a)
-IGNORE=	atlas needs to be built with WITH_STATIC for numpy to function properly
-.endif
+BUILD_DEPENDS+=	${LOCALBASE}/lib/libalapack.a
+@${ECHO_MSG}
+@${ECHO_MSG} "Atlas *must* be built with the WITH_STATIC option"
+@${ECHO_MSG} "for numpy to function correctly. Ensure it is"
+@${ECHO_MSG} "selected in the configuration dialog when prompted, or"
+@${ECHO_MSG} "Ctrl-C now and reinstall the atlas port with the option"
+@${ECHO_MSG} "enabled.
+sleep 5
 .else
 LIB_DEPENDS+=	lapack.4:${PORTSDIR}/math/lapack \
 		blas.2:${PORTSDIR}/math/blas