Minor behavioral fixes

Author: stevapple

Sources/TSCBasic/Process.swift

@@ -334,7 +334,10 @@ public final class Process: ObjectIdentifierProtocol {
             searchPaths.append(AbsolutePath(String(decodingCString: buffer, as: UTF16.self)))
 
             // The 16-bit Windows system directory
-            searchPaths.append(AbsolutePath("\(ProcessEnv.vars["systemdrive"] ?? "C:")\\System"))
+            if let systemDrive = ProcessEnv.vars["systemdrive"],
+               let systemPath = try? AbsolutePath(validating: "\(systemDrive))\\System") {
+                searchPaths.append(systemPath)
+            }
 
             // The Windows directory
             GetWindowsDirectoryW(&buffer, .init(MAX_PATH + 1))

Sources/TSCBasic/misc.swift

@@ -91,7 +91,7 @@ public func lookupExecutablePath(
     guard var value = value, !value.isEmpty else {
         return nil
     }
-    let isPath = value.contains("\\")
+    let isPath = value.contains("\\") || value.contains("/")
     if !isPath && !value.contains(".") {
         value.append(executableFileSuffix)
     }