GASNET_CONFIGURE_ARGS can break UPC++ build

[Dan Bonachea]

GASNet-EX has a very flexible configure space, but UPC++ relies on certain properties that are enabled by default (for example, threading support).

Currently, an unwise envvar setting in GASNET_CONFIGURE_ARGS at UPC++ install time can change these GASNet configure defaults, causing the UPC++ build or operation to break in confusing ways. For example, a value such as GASNET_CONFIGURE_ARGS=--disable-seq will always break the UPC++ install, as will GASNET_CONFIGURE_ARGS=--enable-debug on many platforms.

[Dan Bonachea]

issue #260: prevent GASNET_CONFIGURE_ARGS from breaking UPC++ dependencies

GASNET_CONFIGURE_ARGS was previously too flexible and allowed changing GASNet configure defaults in ways known to break UPC++ installs.

We now enforce the GASNet configure defaults for settings that UPC++ relies upon for correctness of build or operation, to prevent an unwise choice of value from breaking the system in confusing ways.

Fixes issue #260

→ <<cset ba526df3def4>>