Fix python module install destination

We were installing python modules in the wrong locations (and double
installing pyimath).

* Get rid of the double install.
* Make the one install go to the right destination:
  `<install>/lib/pythonX.Y/site-packages`
* With that in place, we can restore the EXPORT that makes
  the python module show up as a target in the exported cmake config.

Signed-off-by: Larry Gritz <lg@larrygritz.com>

src/python/PyImathNumpy/CMakeLists.txt

@@ -22,7 +22,9 @@ if(TARGET Python2::Python AND
     LIBRARY_OUTPUT_NAME "imathnumpy"
     DEBUG_POSTFIX ""
   )
-  install(TARGETS imathnumpy_python2 DESTINATION ${PyImath_Python2_SITEARCH_REL})
+  install(TARGETS imathnumpy_python2
+          DESTINATION "${CMAKE_INSTALL_BINDIR}/python${Python3_VERSION_MAJOR}.${Python3_VERSION_MINOR}/site-packages"
+  )
 endif()
 
 if(TARGET Python3::Python AND
@@ -48,5 +50,7 @@ if(TARGET Python3::Python AND
     LIBRARY_OUTPUT_NAME "imathnumpy"
     DEBUG_POSTFIX ""
   )
-  install(TARGETS imathnumpy_python3 DESTINATION ${PyImath_Python3_SITEARCH_REL})
+  install(TARGETS imathnumpy_python3
+          DESTINATION "${CMAKE_INSTALL_BINDIR}/python${Python3_VERSION_MAJOR}.${Python3_VERSION_MINOR}/site-packages"
+  )
 endif()

src/python/config/ModuleDefine.cmake

@@ -53,12 +53,6 @@ function(PYIMATH_ADD_LIBRARY_PRIV libname)
   )
 
   add_library(${PROJECT_NAME}::${libname} ALIAS ${libname})
-
-  install(TARGETS ${libname}
-    RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
-    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
-    ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
-  )
 endfunction()
 
 # NB: This function has a number if specific names / variables
@@ -130,7 +124,10 @@ function(PYIMATH_DEFINE_MODULE modname)
         LIBRARY_OUTPUT_NAME "${modname}"
         DEBUG_POSTFIX ""
       )
-      install(TARGETS ${modname}_python2 DESTINATION ${PyImath_Python2_SITEARCH_REL})
+      install(TARGETS ${modname}_python2
+              EXPORT ${PROJECT_NAME}
+              DESTINATION "${CMAKE_INSTALL_BINDIR}/python${Python2_VERSION_MAJOR}.${Python2_VERSION_MINOR}/site-packages"
+              )
     endif()
   else()
     if(TARGET Python3::Python)
@@ -157,7 +154,10 @@ function(PYIMATH_DEFINE_MODULE modname)
         LIBRARY_OUTPUT_NAME "${modname}"
         DEBUG_POSTFIX ""
       )
-      install(TARGETS ${modname}_python3 DESTINATION ${PyImath_Python3_SITEARCH_REL})
+      install(TARGETS ${modname}_python3
+              EXPORT ${PROJECT_NAME}
+              DESTINATION "${CMAKE_INSTALL_BINDIR}/python${Python3_VERSION_MAJOR}.${Python3_VERSION_MINOR}/site-packages"
+      )
     endif()
   endif()
 endfunction()