Fix: Run entire build+stage pipeline in single shell invocation

Previous approach used separate Homebrew system() calls for build and
cp, but Ruby cp was not persisting staged binaries between builds.
Now wraps all swift build + cp commands in a single 'sh -c' call.

Author: iamh2o

Formula/wwk.rb

@@ -23,41 +23,29 @@ def install
       }
     SWIFT
 
-    # Swift 6 new build system only keeps the last --product binary
-    # in the output directory.  Build each product and immediately
-    # move it to a staging area using shell cp (Homebrew's Ruby cp
-    # does not execute between system calls in a loop).
-    swift_flags = "--configuration release --disable-sandbox -Xswiftc -cross-module-optimization"
-
+    # Swift 6 new build system may remove previous binaries when
+    # building a different --product.  Run the entire build-and-stage
+    # pipeline in a single shell invocation so nothing interferes.
     staging = buildpath/"staged_binaries"
     staging.mkpath
 
-    # Build wwk, stage it
-    system "swift", "build",
-           "--configuration", "release",
-           "--disable-sandbox",
-           "-Xswiftc", "-cross-module-optimization",
-           "--product", "wwk"
-    bp = Utils.safe_popen_read(
-      "swift", "build", "--show-bin-path", "--configuration", "release"
-    ).chomp
-    system "cp", "#{bp}/wwk", staging.to_s
-
-    # Build wwkd, stage it
-    system "swift", "build",
-           "--configuration", "release",
-           "--disable-sandbox",
-           "-Xswiftc", "-cross-module-optimization",
-           "--product", "wwkd"
-    system "cp", "#{bp}/wwkd", staging.to_s
-
-    # Build WellWhaddyaKnow, stage it
-    system "swift", "build",
-           "--configuration", "release",
-           "--disable-sandbox",
-           "-Xswiftc", "-cross-module-optimization",
-           "--product", "WellWhaddyaKnow"
-    system "cp", "#{bp}/WellWhaddyaKnow", staging.to_s
+    system "sh", "-c", <<~SH
+      set -e
+      FLAGS="--configuration release --disable-sandbox -Xswiftc -cross-module-optimization"
+
+      swift build $FLAGS --product wwk
+      BP=$(swift build --show-bin-path --configuration release)
+      cp "$BP/wwk" "#{staging}/"
+
+      swift build $FLAGS --product wwkd
+      cp "$BP/wwkd" "#{staging}/"
+
+      swift build $FLAGS --product WellWhaddyaKnow
+      cp "$BP/WellWhaddyaKnow" "#{staging}/"
+
+      echo "--- staged_binaries ---"
+      ls -la "#{staging}/"
+    SH
 
     # Install CLI and agent binaries
     bin.install staging/"wwk"