Rename CMake find_package helpers to avoid developer warnings

| CMake Warning (dev) at /usr/share/cmake-3.18/Modules/FindPackageHandleStandardArgs.cmake:273 (message):
|   The package name passed to `find_package_handle_standard_args` (Berkeley)
|   does not match the name of the calling package (BerkeleyDB).  This can lead
|   to problems in calling code that expects `find_package` result variables
|   (e.g., `_FOUND`) to follow a certain pattern.
| Call Stack (most recent call first):
|   CMake/FindBerkeleyDB.cmake:57 (find_package_handle_standard_args)
|   CMakeLists.txt:83 (find_package)
| This warning is for project developers.  Use -Wno-dev to suppress it.

And indeed, we checked for BERKLEY_DB_FOUND which was not defined so our
HAVE_BDB was not set – just that it is never used, so it wasn't noticed.

1 files changed, 25 insertions, 0 deletions

diff --git a/CMake/FindZSTD.cmake b/CMake/FindZSTD.cmake
new file mode 100644
index 000000000..68118049b
--- /dev/null
+++ b/CMake/FindZSTD.cmake
@@ -0,0 +1,25 @@
+# - Try to find ZSTD
+# Once done, this will define
+#
+#  ZSTD_FOUND - system has ZSTD
+#  ZSTD_INCLUDE_DIRS - the ZSTD include directories
+#  ZSTD_LIBRARIES - the ZSTD library
+find_package(PkgConfig)
+
+pkg_check_modules(ZSTD_PKGCONF libzstd)
+
+find_path(ZSTD_INCLUDE_DIRS
+  NAMES zstd.h
+  PATHS ${ZSTD_PKGCONF_INCLUDE_DIRS}
+)
+
+
+find_library(ZSTD_LIBRARIES
+  NAMES zstd
+  PATHS ${ZSTD_PKGCONF_LIBRARY_DIRS}
+)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(ZSTD DEFAULT_MSG ZSTD_INCLUDE_DIRS ZSTD_LIBRARIES)
+
+mark_as_advanced(ZSTD_INCLUDE_DIRS ZSTD_LIBRARIES)