Modify CMakeLists to split up vcpkglib (microsoft#7407)

Before this, we had vcpkg and vcpkg-test taking the vcpkglib source
files directory -- this commit makes vcpkglib an object library.

CMakeLists.txt

@@ -43,14 +43,22 @@ else()
     set(DISABLE_METRICS_VALUE "0")
 endif()
 
-add_executable(vcpkg src/vcpkg.cpp ${VCPKGLIB_SOURCES})
-target_compile_definitions(vcpkg PRIVATE -DDISABLE_METRICS=${DISABLE_METRICS_VALUE})
-target_include_directories(vcpkg PRIVATE include)
-
+add_library(vcpkglib OBJECT ${VCPKGLIB_SOURCES})
+add_executable(vcpkg src/vcpkg.cpp $<TARGET_OBJECTS:vcpkglib>)
+add_executable(vcpkg-test
+    EXCLUDE_FROM_ALL
+    ${VCPKGTEST_SOURCES}
+    $<TARGET_OBJECTS:vcpkglib>)
+
+foreach(TARGET_NAME vcpkglib vcpkg vcpkg-test)
+    target_compile_definitions(${TARGET_NAME} PRIVATE -DDISABLE_METRICS=${DISABLE_METRICS_VALUE})
+    target_include_directories(${TARGET_NAME} PRIVATE include)
+endforeach()
 
-add_executable(vcpkg-test EXCLUDE_FROM_ALL ${VCPKGTEST_SOURCES} ${VCPKGLIB_SOURCES})
-target_compile_definitions(vcpkg-test PRIVATE -DDISABLE_METRICS=${DISABLE_METRICS_VALUE})
-target_include_directories(vcpkg-test PRIVATE include)
+set(THREADS_PREFER_PTHREAD_FLAG ON)
+find_package(Threads REQUIRED)
+target_link_libraries(vcpkg PRIVATE Threads::Threads)
+target_link_libraries(vcpkg-test PRIVATE Threads::Threads)
 
 foreach(TEST_NAME
     arguments chrono dependencies files
@@ -91,8 +99,3 @@ if(MSVC)
   target_sources(vcpkg PRIVATE src/pch.cpp)
   target_compile_options(vcpkg PRIVATE /Yupch.h /FIpch.h /Zm200)
 endif()
-
-set(THREADS_PREFER_PTHREAD_FLAG ON)
-find_package(Threads REQUIRED)
-target_link_libraries(vcpkg PRIVATE Threads::Threads)
-target_link_libraries(vcpkg-test PRIVATE Threads::Threads)