This patch allows the build process to use the provided dependencies instead
of adding their source as CMake sub-directories (in which case "make install"
would install googletest's and googlebenchmark's libraries and headers).

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5e7d127..4b269b9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -28,7 +28,7 @@ MACRO(FP16_TARGET_ENABLE_CXX11 target)
 ENDMACRO()
 
 # ---[ Download deps
-IF(NOT DEFINED PSIMD_SOURCE_DIR)
+IF(FALSE)
   MESSAGE(STATUS "Downloading PSimd to ${CMAKE_BINARY_DIR}/psimd-source (define PSIMD_SOURCE_DIR to avoid it)")
   CONFIGURE_FILE(cmake/DownloadPSimd.cmake "${CMAKE_BINARY_DIR}/psimd-download/CMakeLists.txt")
   EXECUTE_PROCESS(COMMAND "${CMAKE_COMMAND}" -G "${CMAKE_GENERATOR}" .
@@ -38,7 +38,7 @@ IF(NOT DEFINED PSIMD_SOURCE_DIR)
   SET(PSIMD_SOURCE_DIR "${CMAKE_BINARY_DIR}/psimd-source" CACHE STRING "PSimd source directory")
 ENDIF()
 
-IF(FP16_BUILD_TESTS AND NOT DEFINED GOOGLETEST_SOURCE_DIR)
+IF(FALSE)
   MESSAGE(STATUS "Downloading Google Test to ${CMAKE_BINARY_DIR}/googletest-source (define GOOGLETEST_SOURCE_DIR to avoid it)")
   CONFIGURE_FILE(cmake/DownloadGoogleTest.cmake "${CMAKE_BINARY_DIR}/googletest-download/CMakeLists.txt")
   EXECUTE_PROCESS(COMMAND "${CMAKE_COMMAND}" -G "${CMAKE_GENERATOR}" .
@@ -48,7 +48,7 @@ IF(FP16_BUILD_TESTS AND NOT DEFINED GOOGLETEST_SOURCE_DIR)
   SET(GOOGLETEST_SOURCE_DIR "${CMAKE_BINARY_DIR}/googletest-source" CACHE STRING "Google Test source directory")
 ENDIF()
 
-IF(FP16_BUILD_BENCHMARKS AND NOT DEFINED GOOGLEBENCHMARK_SOURCE_DIR)
+IF(FALSE)
   MESSAGE(STATUS "Downloading Google Benchmark to ${CMAKE_BINARY_DIR}/googlebenchmark-source (define GOOGLEBENCHMARK_SOURCE_DIR to avoid it)")
   CONFIGURE_FILE(cmake/DownloadGoogleBenchmark.cmake "${CMAKE_BINARY_DIR}/googlebenchmark-download/CMakeLists.txt")
   EXECUTE_PROCESS(COMMAND "${CMAKE_COMMAND}" -G "${CMAKE_GENERATOR}" .
@@ -84,22 +84,7 @@ INSTALL(FILES
     include/fp16/avx2.py
   DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/fp16)
 
-# ---[ Configure psimd
-IF(NOT TARGET psimd)
-  ADD_SUBDIRECTORY(
-    "${PSIMD_SOURCE_DIR}"
-    "${CMAKE_BINARY_DIR}/psimd")
-ENDIF()
-
 IF(FP16_BUILD_TESTS)
-  # ---[ Build google test
-  IF(NOT TARGET gtest)
-    SET(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
-    ADD_SUBDIRECTORY(
-      "${GOOGLETEST_SOURCE_DIR}"
-      "${CMAKE_BINARY_DIR}/googletest")
-  ENDIF()
-
   # ---[ Build FP16 unit tests
   ADD_EXECUTABLE(ieee-to-fp32-bits-test test/ieee-to-fp32-bits.cc test/tables.cc)
   TARGET_INCLUDE_DIRECTORIES(ieee-to-fp32-bits-test PRIVATE test)
@@ -137,40 +122,32 @@ IF(FP16_BUILD_TESTS)
 ENDIF()
 
 IF(FP16_BUILD_BENCHMARKS)
-  # ---[ Build google benchmark
-  IF(NOT TARGET benchmark)
-    SET(BENCHMARK_ENABLE_TESTING OFF CACHE BOOL "")
-    ADD_SUBDIRECTORY(
-      "${GOOGLEBENCHMARK_SOURCE_DIR}"
-      "${CMAKE_BINARY_DIR}/googlebenchmark")
-  ENDIF()
-
   # ---[ Build FP16 benchmarks
   ADD_EXECUTABLE(ieee-element-bench bench/ieee-element.cc)
   TARGET_COMPILE_DEFINITIONS(ieee-element-bench PRIVATE FP16_COMPARATIVE_BENCHMARKS=1)
   TARGET_INCLUDE_DIRECTORIES(ieee-element-bench PRIVATE ${PROJECT_SOURCE_DIR})
-  TARGET_LINK_LIBRARIES(ieee-element-bench fp16 psimd benchmark)
+  TARGET_LINK_LIBRARIES(ieee-element-bench fp16 benchmark)
 
   ADD_EXECUTABLE(alt-element-bench bench/alt-element.cc)
-  TARGET_LINK_LIBRARIES(alt-element-bench fp16 psimd benchmark)
+  TARGET_LINK_LIBRARIES(alt-element-bench fp16 benchmark)
 
   ADD_EXECUTABLE(from-ieee-array-bench bench/from-ieee-array.cc)
   FP16_TARGET_ENABLE_CXX11(from-ieee-array-bench)
   TARGET_COMPILE_DEFINITIONS(from-ieee-array-bench PRIVATE FP16_COMPARATIVE_BENCHMARKS=1)
   TARGET_INCLUDE_DIRECTORIES(from-ieee-array-bench PRIVATE ${PROJECT_SOURCE_DIR})
-  TARGET_LINK_LIBRARIES(from-ieee-array-bench fp16 psimd benchmark)
+  TARGET_LINK_LIBRARIES(from-ieee-array-bench fp16 benchmark)
 
   ADD_EXECUTABLE(from-alt-array-bench bench/from-alt-array.cc)
   FP16_TARGET_ENABLE_CXX11(from-alt-array-bench)
-  TARGET_LINK_LIBRARIES(from-alt-array-bench fp16 psimd benchmark)
+  TARGET_LINK_LIBRARIES(from-alt-array-bench fp16 benchmark)
 
   ADD_EXECUTABLE(to-ieee-array-bench bench/to-ieee-array.cc)
   FP16_TARGET_ENABLE_CXX11(to-ieee-array-bench)
   TARGET_COMPILE_DEFINITIONS(to-ieee-array-bench PRIVATE FP16_COMPARATIVE_BENCHMARKS=1)
   TARGET_INCLUDE_DIRECTORIES(to-ieee-array-bench PRIVATE ${PROJECT_SOURCE_DIR})
-  TARGET_LINK_LIBRARIES(to-ieee-array-bench fp16 psimd benchmark)
+  TARGET_LINK_LIBRARIES(to-ieee-array-bench fp16 benchmark)
 
   ADD_EXECUTABLE(to-alt-array-bench bench/to-alt-array.cc)
   FP16_TARGET_ENABLE_CXX11(to-alt-array-bench)
-  TARGET_LINK_LIBRARIES(to-alt-array-bench fp16 psimd benchmark)
+  TARGET_LINK_LIBRARIES(to-alt-array-bench fp16 benchmark)
 ENDIF()