CMakeLists: Fix logic of BUILD_CPPDAP

set() does not evaluate conditional expressions like if() does.
BUILD_CPPDAP was being set to "${BUILD_VULKAN};AND;${ENABLE_VULKAN_DEBUGGER}", so cppdap was always required as a submodule dependency.

Bug: b/145351270
Change-Id: I86c3e43b8e22aa283bd2a5a20e0c03c01a965e8a
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/39310
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Tested-by: Ben Clayton <bclayton@google.com>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6d4bb75..f27ee1e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -109,7 +109,12 @@
 option(ENABLE_VULKAN_DEBUGGER "Enable vulkan debugger support" 0)
 
 set(BUILD_MARL ${BUILD_VULKAN})
-set(BUILD_CPPDAP ${BUILD_VULKAN} AND ${ENABLE_VULKAN_DEBUGGER})
+
+if(${BUILD_VULKAN} AND ${ENABLE_VULKAN_DEBUGGER})
+    set(BUILD_CPPDAP 1)
+else()
+    set(BUILD_CPPDAP 0)
+endif()
 
 set(DEFAULT_REACTOR_BACKEND "LLVM")