tools/cmake: fix compilation with host libzstd-dev

cmake's find_package looks at host paths first for some reason. Switch
to using pkgconfig for the search, matching other modules.

Fixes: 3848cf45 ("tools/cmake: Build without some included libs")
Signed-off-by: Rosen Penev <rosenp@gmail.com>

tools/cmake/patches/150-zstd-libarchive.patch

+--- a/Utilities/cmlibarchive/CMakeLists.txt
++++ b/Utilities/cmlibarchive/CMakeLists.txt
+@@ -630,8 +630,13 @@ IF(ENABLE_ZSTD)
+     SET(ZSTD_FIND_QUIETLY TRUE)
+   ENDIF (ZSTD_INCLUDE_DIR)
+ 
+-  FIND_PATH(ZSTD_INCLUDE_DIR zstd.h)
+-  FIND_LIBRARY(ZSTD_LIBRARY NAMES zstd libzstd)
++  IF(UNIX)
++  FIND_PACKAGE(PkgConfig QUIET)
++  PKG_SEARCH_MODULE(PC_ZSTD libzstd)
++  ENDIF()
++
++  FIND_PATH(ZSTD_INCLUDE_DIR zstd.h HINTS ${PC_ZSTD_INCLUDEDIR} ${PC_ZSTD_INCLUDE_DIRS})
++  FIND_LIBRARY(ZSTD_LIBRARY NAMES zstd HINTS ${PC_ZSTD_LIBDIR} ${PC_ZSTD_LIBRARY_DIRS})
+   INCLUDE(FindPackageHandleStandardArgs)
+   FIND_PACKAGE_HANDLE_STANDARD_ARGS(ZSTD DEFAULT_MSG ZSTD_LIBRARY ZSTD_INCLUDE_DIR)
+ ELSE(ENABLE_ZSTD)