build: ptex support for static library (#4072)

In some environments, only one kind of the library could be available.
Choose proper fallback in such cases. Prefer static library, if
LINKSTATIC is ON and dynamic otherwise.

Signed-off-by: Dominik Wójt <domin144@o2.pl>

src/ptex.imageio/CMakeLists.txt

@@ -3,7 +3,11 @@
 # https://github.com/AcademySoftwareFoundation/OpenImageIO
 
 if (Ptex_FOUND)
+    set(ptex_target Ptex::Ptex_dynamic)
+    if (TARGET Ptex::Ptex_static AND (NOT TARGET Ptex::Ptex_dynamic OR LINKSTATIC))
+        set(ptex_target Ptex::Ptex_static)
+    endif()
     add_oiio_plugin (ptexinput.cpp
-                     LINK_LIBRARIES Ptex::Ptex_dynamic ZLIB::ZLIB
+                     LINK_LIBRARIES ${ptex_target} ZLIB::ZLIB
                      DEFINITIONS "-DUSE_PTEX")
 endif ()