Bad PTX ISA version when using LLVM 6 or greater

[elliottslaughter]

The solver builds successfully on LLVM 6, but when we run test cases, this error occurs:

Invoking Legion on 1 rank(s), 1 node(s) (1 rank(s) per node), as follows:
/home/hpcc/cmelone/insieme/builds/890523826/HTR-solver/src/prometeo_ConstPropMix.exec -i TaylorGreen2D_16.json -o 16 -ll:cpu 1 -ll:ocpu 2 -ll:onuma 1 -ll:othr 9 -ll:ostack 8 -ll:gpu 1 -ll:fsize 4000 -ll:zsize 512 -ll:ib_zsize 512 -ll:util 2 -ll:io 1 -ll:bgwork 2 -ll:cpu_bgwork 100 -ll:util_bgwork 100 -ll:csize 220000 -ll:rsize 512 -ll:ib_rsize 512 -ll:gsize 0 -ll:stacksize 8 -lg:sched -1 -lg:hysteresis 0
[0 - 7f0af0f41840]    0.744143 {5}{gpu}: Failed to load CUDA module! Error log: ptxas application ptx input, line 29155; error   : Feature 'rsqrt.approx.ftz.f64' requires PTX ISA .version 4.0 or later
ptxas application ptx input, line 29279; error   : Feature 'rsqrt.approx.ftz.f64' requires PTX ISA .version 4.0 or later
ptxas application ptx input, line 29440; error   : Feature 'rsqrt.approx.ftz.f64' requires PTX ISA .version 4.0 or later
ptxas application ptx input, line 29709; error   : Feature 'rsqrt.approx.ftz.f64' requires PTX ISA .version 4.0 or later
ptxas application ptx input, line 30067; error   : Feature 'rsqrt.approx.ftz.f64' requires PTX ISA .version 4.0 or later
ptxas application ptx input, line 30129; error   : Feature 'rsqrt.approx.ftz.f64' requires PTX ISA .version 4.0 or later
ptxas application ptx input, line 30206; error   : Feature 'rsqrt.approx.ftz.f64' requires PTX ISA .version 4.0 or later
ptxas application ptx input, line 30270; error   : Feature 'rsqrt.approx.ftz.f64' requires PTX ISA .version 4.0 or later
ptxas application ptx input, line 30336; error   : Feature 'rsqrt.approx.ftz.f64' requires PTX ISA .version 4.0 or later
ptxas application ptx input, line 30408; error   : Feature 'rsqrt.approx.ftz.f64' requires PTX ISA .version 4.0 or later
ptxas application ptx input, line 30502; error   : Feature 'rsqrt.approx.ftz.f64' requires PTX ISA .version 4.0 or later
ptxas application ptx input, line 36620; error   : Feature 'rsqrt.approx.ftz.f64' requires PTX ISA .version 4.0 or later
ptxas application ptx input, line 36753; error   : Feature 'rsqrt.approx.ftz.f64' requires PTX ISA .version 4.0 or later
ptxas application ptx input, line 37325; error   : Feature 'rsqrt.approx.ftz.f64' requires PTX ISA .version 4.0 or later
ptxas application ptx input, line 37604; error   : Feature 'rsqrt.approx.ftz.f64' requires PTX ISA .version 4.0 or later
ptxas fatal   : Ptx assembly aborted due to errors

I'm not sure how related this is directly to terra, but this is an issue we encounter on 6.0 and not 3.8

Originally posted by @cmelone in #471 (comment)

[elliottslaughter]

I've been told that this issue no longer reproduces, so I'm closing this.