Use find_package to search for system lz4 before vendoring

Builds/CMake/deps/Findlz4.cmake

@@ -0,0 +1,22 @@
+find_package (PkgConfig REQUIRED)
+pkg_search_module (lz4_PC QUIET liblz4>=1.8)
+
+if(static)
+  set(LZ4_LIB liblz4.a)
+else()
+  set(LZ4_LIB lz4)
+endif()
+
+find_library (lz4
+  NAMES ${LZ4_LIB}
+  HINTS
+    ${lz4_PC_LIBDIR}
+    ${lz4_PC_LIBRARY_DIRS}
+  NO_DEFAULT_PATH)
+
+find_path (LZ4_INCLUDE_DIR
+  NAMES lz4.h
+  HINTS
+    ${lz4_PC_INCLUDEDIR}
+    ${lz4_PC_INCLUDEDIRS}
+  NO_DEFAULT_PATH)

Builds/CMake/deps/Libarchive.cmake

@@ -73,7 +73,7 @@ ExternalProject_Add (libarchive
       >
   TEST_COMMAND ""
   INSTALL_COMMAND ""
-  DEPENDS lz4
+  DEPENDS lz4_lib
   BUILD_BYPRODUCTS
     <BINARY_DIR>/libarchive/${ep_lib_prefix}archive${lib_post}${ep_lib_suffix}
     <BINARY_DIR>/libarchive/${ep_lib_prefix}archive${lib_post}_d${ep_lib_suffix}

Builds/CMake/deps/Lz4.cmake

@@ -2,58 +2,77 @@
    NIH dep: lz4
 #]===================================================================]
 
-ExternalProject_Add (lz4
-  PREFIX ${nih_cache_path}
-  GIT_REPOSITORY https://github.com/lz4/lz4.git
-  GIT_TAG v1.8.2
-  SOURCE_SUBDIR contrib/cmake_unofficial
-  CMAKE_ARGS
-    -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}
-    -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER}
-    $<$<BOOL:${CMAKE_VERBOSE_MAKEFILE}>:-DCMAKE_VERBOSE_MAKEFILE=ON>
-    -DCMAKE_DEBUG_POSTFIX=_d
-    $<$<NOT:$<BOOL:${is_multiconfig}>>:-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}>
-    -DBUILD_STATIC_LIBS=ON
-    -DBUILD_SHARED_LIBS=OFF
-    $<$<BOOL:${MSVC}>:
-      "-DCMAKE_C_FLAGS=-GR -Gd -fp:precise -FS -MP"
-      "-DCMAKE_C_FLAGS_DEBUG=-MTd"
-      "-DCMAKE_C_FLAGS_RELEASE=-MT"
-    >
-  LOG_BUILD ON
-  LOG_CONFIGURE ON
-  BUILD_COMMAND
-    ${CMAKE_COMMAND}
-    --build .
-    --config $<CONFIG>
-    --target lz4_static
-    $<$<VERSION_GREATER_EQUAL:${CMAKE_VERSION},3.12>:--parallel ${ep_procs}>
-    $<$<BOOL:${is_multiconfig}>:
-      COMMAND
-        ${CMAKE_COMMAND} -E copy
-        <BINARY_DIR>/$<CONFIG>/${ep_lib_prefix}lz4$<$<CONFIG:Debug>:_d>${ep_lib_suffix}
-        <BINARY_DIR>
-      >
-  TEST_COMMAND ""
-  INSTALL_COMMAND ""
-  BUILD_BYPRODUCTS
-    <BINARY_DIR>/${ep_lib_prefix}lz4${ep_lib_suffix}
-    <BINARY_DIR>/${ep_lib_prefix}lz4_d${ep_lib_suffix}
-)
-ExternalProject_Get_Property (lz4 BINARY_DIR)
-ExternalProject_Get_Property (lz4 SOURCE_DIR)
-if (CMAKE_VERBOSE_MAKEFILE)
-  print_ep_logs (lz4)
-endif ()
 add_library (lz4_lib STATIC IMPORTED GLOBAL)
-file (MAKE_DIRECTORY ${SOURCE_DIR}/lz4)
-set_target_properties (lz4_lib PROPERTIES
-  IMPORTED_LOCATION_DEBUG
-    ${BINARY_DIR}/${ep_lib_prefix}lz4_d${ep_lib_suffix}
-  IMPORTED_LOCATION_RELEASE
-    ${BINARY_DIR}/${ep_lib_prefix}lz4${ep_lib_suffix}
-  INTERFACE_INCLUDE_DIRECTORIES
-    ${SOURCE_DIR}/lib)
+
+if (NOT WIN32)
+  find_package(lz4)
+endif()
+
+if(lz4)
+  set_target_properties (lz4_lib PROPERTIES
+    IMPORTED_LOCATION_DEBUG
+      ${lz4}
+    IMPORTED_LOCATION_RELEASE
+      ${lz4}
+    INTERFACE_INCLUDE_DIRECTORIES
+      ${LZ4_INCLUDE_DIR})
+
+else()
+  ExternalProject_Add (lz4
+    PREFIX ${nih_cache_path}
+    GIT_REPOSITORY https://github.com/lz4/lz4.git
+    GIT_TAG v1.8.2
+    SOURCE_SUBDIR contrib/cmake_unofficial
+    CMAKE_ARGS
+      -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}
+      -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER}
+      $<$<BOOL:${CMAKE_VERBOSE_MAKEFILE}>:-DCMAKE_VERBOSE_MAKEFILE=ON>
+      -DCMAKE_DEBUG_POSTFIX=_d
+      $<$<NOT:$<BOOL:${is_multiconfig}>>:-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}>
+      -DBUILD_STATIC_LIBS=ON
+      -DBUILD_SHARED_LIBS=OFF
+      $<$<BOOL:${MSVC}>:
+        "-DCMAKE_C_FLAGS=-GR -Gd -fp:precise -FS -MP"
+        "-DCMAKE_C_FLAGS_DEBUG=-MTd"
+        "-DCMAKE_C_FLAGS_RELEASE=-MT"
+      >
+    LOG_BUILD ON
+    LOG_CONFIGURE ON
+    BUILD_COMMAND
+      ${CMAKE_COMMAND}
+      --build .
+      --config $<CONFIG>
+      --target lz4_static
+      $<$<VERSION_GREATER_EQUAL:${CMAKE_VERSION},3.12>:--parallel ${ep_procs}>
+      $<$<BOOL:${is_multiconfig}>:
+        COMMAND
+          ${CMAKE_COMMAND} -E copy
+          <BINARY_DIR>/$<CONFIG>/${ep_lib_prefix}lz4$<$<CONFIG:Debug>:_d>${ep_lib_suffix}
+          <BINARY_DIR>
+        >
+    TEST_COMMAND ""
+    INSTALL_COMMAND ""
+    BUILD_BYPRODUCTS
+      <BINARY_DIR>/${ep_lib_prefix}lz4${ep_lib_suffix}
+      <BINARY_DIR>/${ep_lib_prefix}lz4_d${ep_lib_suffix}
+  )
+  ExternalProject_Get_Property (lz4 BINARY_DIR)
+  ExternalProject_Get_Property (lz4 SOURCE_DIR)
+
+  file (MAKE_DIRECTORY ${SOURCE_DIR}/lz4)
+  set_target_properties (lz4_lib PROPERTIES
+    IMPORTED_LOCATION_DEBUG
+      ${BINARY_DIR}/${ep_lib_prefix}lz4_d${ep_lib_suffix}
+    IMPORTED_LOCATION_RELEASE
+      ${BINARY_DIR}/${ep_lib_prefix}lz4${ep_lib_suffix}
+    INTERFACE_INCLUDE_DIRECTORIES
+      ${SOURCE_DIR}/lib)
+
+  if (CMAKE_VERBOSE_MAKEFILE)
+    print_ep_logs (lz4)
+  endif ()
+endif()
+
 add_dependencies (lz4_lib lz4)
 target_link_libraries (ripple_libs INTERFACE lz4_lib)
 exclude_if_included (lz4)

Builds/CMake/deps/Rocksdb.cmake

@@ -84,7 +84,7 @@ ExternalProject_Add (rocksdb
   LIST_SEPARATOR ::
   TEST_COMMAND ""
   INSTALL_COMMAND ""
-  DEPENDS snappy lz4
+  DEPENDS snappy lz4_lib
   BUILD_BYPRODUCTS
     <BINARY_DIR>/${ep_lib_prefix}rocksdb${ep_lib_suffix}
     <BINARY_DIR>/${ep_lib_prefix}rocksdb_d${ep_lib_suffix}