Ensure that the PEX_ROOT is always a realpath. #3278

Job	Run time
Check GitHub Organization	1s
tox -e format-check,lint-check,typecheck,enum-check,vendor-check,package,docs	11m 31s
./dtox.sh -e py27-pip20	9m 57s
tox -e py313-pip24_3_1	16m 25s
./dtox.sh -e py38-pip22_3_1	18m 1s
tox -e py313-pip24_3_1-integration --shard 1/2	24m 0s
./dtox.sh -e py311-pip23_3_2	18m 34s
tox -e py313-pip24_3_1-integration --shard 2/2	26m 30s
./dtox.sh -e py313-pip24_3_1	14m 6s
./dtox.sh -e py314-pip24_3_1	14m 42s
./dtox.sh -e pypy310-pip24_3_1	27m 51s
./dtox.sh -e py27-pip20-integration	28m 34s
./dtox.sh -e py38-pip22_3_1-integration --shard 1/2	30m 26s
./dtox.sh -e py38-pip22_3_1-integration --shard 2/2	28m 28s
./dtox.sh -e py311-pip23_3_2-integration --shard 1/2	30m 43s
./dtox.sh -e py311-pip23_3_2-integration --shard 2/2	29m 15s
./dtox.sh -e py313-pip24_3_1-integration --shard 1/2	27m 28s
./dtox.sh -e py313-pip24_3_1-integration --shard 2/2	27m 38s
./dtox.sh -e py314-pip24_3_1-integration --shard 1/2	29m 48s
./dtox.sh -e py314-pip24_3_1-integration --shard 2/2	26m 32s
./dtox.sh -e pypy310-pip24_3_1-integration --shard 1/2	47m 42s
./dtox.sh -e pypy310-pip24_3_1-integration --shard 2/2	49m 11s
Gather Final Status	1s
	8h 57m 24s

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