[CMake] Create ChemistryLib.

ChemistryLib/CMakeLists.txt

+#Source files grouped by a directory
+get_source_files(SOURCES)
+append_source_files(SOURCES PhreeqcIOData)
+
+# Create the library
+add_library(ChemistryLib ${SOURCES})
+if(BUILD_SHARED_LIBS)
+    install(TARGETS ChemistryLib LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR})
+endif()
+
+include(GenerateExportHeader)
+generate_export_header(ChemistryLib)
+
+target_link_libraries(ChemistryLib
+    PUBLIC iphreeqc
+    PRIVATE NumLib
+)
+
+if(OGS_USE_PCH)
+    cotire(ChemistryLib)
+endif()