Fix b with zsh (again), remove shwordsplit use.

Context: zsh doesn't do string splitting like bash, so it passes the
post-processed bazel args to bazel as a single arg. So this CL adds a
conditional to split explicitly with zsh using the {=<arg>} flag
syntax.

Reference: https://zsh.sourceforge.io/FAQ/zshfaq03.html (for shwordsplit)
Reference: https://zsh.sourceforge.io/Guide/zshguide05.html (Section 5.4.4)

For bash, this uses array[@] to split the list into separate
shell words.

Test: zsh; source build/envsetup.sh && b test
//system/logging/logd:logd-unit-tests --config=linux_x86_64
Test: bash; source build/envsetup.sh && b test
//system/logging/logd:logd-unit-tests --config=linux_x86_64

Change-Id: Id92462661bbe1799a6de8dd3393799d91e3044e8

envsetup.sh

@@ -1858,7 +1858,7 @@ function b()
     _trigger_build "all-modules" bp2build $skip_tests USE_BAZEL_ANALYSIS= || return 1
     # Then, run Bazel using the synthetic workspace as the --package_path.
     if [[ -z "$bazel_args" ]]; then
-        # If there are no args, show help.
+        # If there are no args, show help and exit.
         bazel help
     else
         # Else, always run with the bp2build configuration, which sets Bazel's package path to the synthetic workspace.
@@ -1882,14 +1882,16 @@ function b()
             bazel_args_with_config+=("--config=bp2build ")
         fi
 
+        # Call Bazel.
         if [ -n "$ZSH_VERSION" ]; then
             # zsh breaks posix by not doing string-splitting on unquoted args
-          # by default. Enable the compatibility option.
-          setopt shwordsplit
-        fi
-        # Call Bazel.
+            # by default. Explicitly use the "=" flag to split.
+            # See https://zsh.sourceforge.io/Guide/zshguide05.html section 5.4.4.
+            bazel ${=bazel_args_with_config}
+        else
             bazel ${bazel_args_with_config[@]}
         fi
+    fi
 )
 
 function m()