tests: Remove unneeded build step from nightly.sh

The `main.py` script will build the ISAs required to run tests. Our
compiler tests (see "tests/compiler-tests.sh") are run nightly and
already test to ensure these ISAs are compiled correctly. Compiling
these ISAs as part of this script is therefore redundant. This patch
removes this step to save testing time.

Change-Id: I58636acfd5512886ac11ca84ee96cbdc9e344c68
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/65175
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

tests/nightly.sh

@@ -61,20 +61,6 @@ if [[ "$gpu_isa" != "GCN3_X86" ]] && [[ "$gpu_isa" != "VEGA_X86" ]]; then
     exit 1
 fi
 
-build_target () {
-    isa=$1
-
-    # Try to build. If not, delete the build directory and try again.
-    # SCons is not perfect, and occasionally does not catch a necessary
-    # compilation: https://gem5.atlassian.net/browse/GEM5-753
-    docker run -u $UID:$GID --volume "${gem5_root}":"${gem5_root}" -w \
-        "${gem5_root}" --memory="${docker_mem_limit}" --rm \
-        gcr.io/gem5-test/ubuntu-22.04_all-dependencies:latest \
-            bash -c "scons build/${isa}/gem5.opt -j${compile_threads} \
-            --ignore-style || (rm -rf build && scons build/${isa}/gem5.opt \
-            -j${compile_threads} --ignore-style)"
-}
-
 unit_test () {
     build=$1
 
@@ -88,15 +74,6 @@ unit_test () {
 # Ensure we have the latest docker images.
 docker pull gcr.io/gem5-test/ubuntu-22.04_all-dependencies:latest
 
-# Try to build the ISA targets.
-build_target NULL
-build_target RISCV
-build_target X86
-build_target ARM
-build_target SPARC
-build_target MIPS
-build_target POWER
-
 # Run the unit tests.
 unit_test opt
 unit_test debug