LocalJDKLauncher hard-codes `/bin/java` and does not build a Windows Java executable path

[shaaravraghu]

Type
Bug

Severity
High

Modules

• spawn-local-jdk

Evidence

• spawn-local-jdk/src/main/java/build/spawn/platform/local/jdk/LocalJDKLauncher.java:75-78
• getExecutable(...) returns Executable.of(options.get(JDKHome.class).get() + "/bin/java").

Why this matters

• The project includes Windows-aware JDK detection logic, so local JDK launching appears intended to be cross-platform.
• A hard-coded Unix-style executable path breaks Windows usage where the binary is typically bin\\java.exe.

Expected behavior

• The Java executable path should be constructed with platform-aware path resolution.

Actual behavior

• The launcher always concatenates a Unix-style suffix.

Suggested reproduction

1. Resolve a Windows JDKHome.
2. Launch a JDKApplication through LocalJDKLauncher.
3. Observe that the executable path points to /bin/java rather than bin\\java.exe.

Suggested fix

• Build the executable path with Path.resolve(...).
• Append java.exe on Windows and java elsewhere, or rely on ProcessBuilder with the resolved Path.

Suggested tests

• Add an OS-specific unit test for executable resolution on Windows.
• Add a cross-platform test that asserts the executable path is normalized from JDKHome.

Issue body ready to paste
LocalJDKLauncher.getExecutable(...) hard-codes the Java binary as JDKHome + "/bin/java". That works on Unix-like systems but breaks Windows launches, even though the surrounding module already contains Windows-aware JDK detection logic.`