tests: replace all GPU uses of GUID with GID

As part of the docker commands for square and HeteroSync, the READMEs
suggest to use GUID.  However, this does not exist.  This commit fixes
the problem by replacing with GID.

Change-Id: Ia80b4d243548fd78c9589e0caaddb9de71c532c5
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-resources/+/51587
Maintainer: Matt Sinclair <mattdsinclair@gmail.com>
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: Bobby R. Bruce <bbruce@ucdavis.edu>
diff --git a/src/gpu/heterosync/README.md b/src/gpu/heterosync/README.md
index 07f620d..c7c3d51 100644
--- a/src/gpu/heterosync/README.md
+++ b/src/gpu/heterosync/README.md
@@ -33,7 +33,7 @@
 HeteroSync has multiple applications that can be run (see below).  For example, to run sleepMutex with 10 ld/st per thread, 16 WGs, and 4 iterations of the critical section:
 
 ```
-docker run -u $UID:$GUID --volume $(pwd):$(pwd) -w $(pwd) gcr.io/gem5-test/gcn-gpu:latest gem5/build/GCN3_X86/gem5.opt gem5/configs/example/apu_se.py -n 3 -c bin/allSyncPrims-1kernel --options="sleepMutex 10 16 4"
+docker run -u $UID:$GID --volume $(pwd):$(pwd) -w $(pwd) gcr.io/gem5-test/gcn-gpu:latest gem5/build/GCN3_X86/gem5.opt gem5/configs/example/apu_se.py -n 3 -c bin/allSyncPrims-1kernel --options="sleepMutex 10 16 4"
 ```
 
 ## Pre-built binary
diff --git a/src/gpu/square/README.md b/src/gpu/square/README.md
index 3ca07e3..28db907 100644
--- a/src/gpu/square/README.md
+++ b/src/gpu/square/README.md
@@ -34,11 +34,11 @@
 ```
 git clone https://gem5.googlesource.com/public/gem5
 cd gem5
-docker run -u $UID:$GUID --volume $(pwd):$(pwd) -w $(pwd) gcr.io/gem5-test/gcn-gpu:latest scons build/GCN3_X86/gem5.opt -j <num cores>
+docker run -u $UID:$GID --volume $(pwd):$(pwd) -w $(pwd) gcr.io/gem5-test/gcn-gpu:latest scons build/GCN3_X86/gem5.opt -j <num cores>
 ```
 
 ## Running Square on GCN3_X86/gem5.opt
 
 ```
-docker run -u $UID:$GUID --volume $(pwd):$(pwd) -w $(pwd) gcr.io/gem5-test/gcn-gpu:latest gem5/build/GCN3_X86/gem5.opt gem5/configs/example/apu_se.py -n 3 -c bin/square
+docker run -u $UID:$GID --volume $(pwd):$(pwd) -w $(pwd) gcr.io/gem5-test/gcn-gpu:latest gem5/build/GCN3_X86/gem5.opt gem5/configs/example/apu_se.py -n 3 -c bin/square
 ```