ci: sanitizers - shell:bash for steps that use 'source'

The test-deps container's default shell is dash (Debian's /bin/sh),
not bash. 'source' is a bash builtin - dash has no such command, so
the sanitizers step exits 127 with 'source: not found' before the
actual test runs (job 78146645114).

Add 'shell: bash' to the three steps in sanitizers.yml that source
scripts/env-setup (ASan job test + cmd-tests, TSan job test). Other
PR-time workflows that use 'source scripts/env-setup' (cmdline,
fips-ready) run on the host ubuntu-22.04 runner where bash is the
default, so they don't need this fix.

Author: aidangarske

.github/workflows/sanitizers.yml

@@ -90,12 +90,15 @@ jobs:
             ./scripts/build-wolfprovider.sh
 
       - name: Run wolfprov unit tests (make test) under sanitizers
+        # bash needed for `source` - container default shell is dash.
+        shell: bash
         run: |
           export LD_PRELOAD="$(gcc -print-file-name=libasan.so)"
           source scripts/env-setup
           make test
 
       - name: Run cmd-tests under sanitizers
+        shell: bash
         run: |
           export LD_PRELOAD="$(gcc -print-file-name=libasan.so)"
           source scripts/env-setup
@@ -170,6 +173,7 @@ jobs:
             ./scripts/build-wolfprovider.sh
 
       - name: Run wolfprov unit tests (make test) under TSan
+        shell: bash
         run: |
           # `|| true`: env-setup's provider check fails under TSan
           # (stock openssl can't dlopen a TSan-instrumented provider).