Add gtest_main.cc to libgtest.a

Currently when compiling GoogleTest from source code, source file
gtest_main.cc from GoogleTest repository is not compiled into any
library as in GoogleTest repository, where it is compiled into
libgtest_main.a. Instead gtest_main.cc is added to source file list
GTEST_SRC, which is then added to the list of source files of every
single GoogleTest based test application.

To simplify this gtest_main.cc is added to the source file list of
target gtest now. Additionally GTEST_SRC is merged into
lib_gtest_SOURCES, since both variables defined source files for
GoogleTest libraries.

Now target gtest generates library libgtest.a, which already contains
the main function from source file gtest_main.cc. This is different to
GoogleTest build system, where both are separated into two independent
libraries libgtest.a and libgtest_main.a.

libgnucash/core-utils/test/CMakeLists.txt

@@ -47,8 +47,7 @@ set(test_gnc_path_util_SOURCES
   ${MODULEPATH}/binreloc.c
   ${MODULEPATH}/gnc-filepath-utils.cpp
   ${MODULEPATH}/gnc-locale-utils.cpp
-  gtest-path-utilities.cpp
-  ${GTEST_SRC})
+  gtest-path-utilities.cpp)
 
 gnc_add_test(test-gnc-path-util "${test_gnc_path_util_SOURCES}"
   gtest_core_utils_INCLUDES gtest_core_utils_LIBS "GNC_UNINSTALLED=yes")

libgnucash/engine/test/CMakeLists.txt

@@ -122,30 +122,26 @@ endif (WIN32)
 
 set(test_gnc_guid_SOURCES
   ${MODULEPATH}/guid.cpp
-  test-gnc-guid.cpp
-  ${GTEST_SRC})
+  test-gnc-guid.cpp)
 gnc_add_test(test-gnc-guid "${test_gnc_guid_SOURCES}"
   gtest_engine_INCLUDES gtest_old_engine_LIBS)
 
 set(test_kvp_value_SOURCES
   ${MODULEPATH}/kvp-value.cpp
   test-kvp-value.cpp
-  test-kvp-frame.cpp
-  ${GTEST_SRC})
+  test-kvp-frame.cpp)
 gnc_add_test(test-kvp-value "${test_kvp_value_SOURCES}"
   gtest_engine_INCLUDES gtest_old_engine_LIBS)
 
 set(test_qofsession_SOURCES
   ${MODULEPATH}/qofsession.cpp
-  test-qofsession.cpp
-  ${GTEST_SRC})
+  test-qofsession.cpp)
 gnc_add_test(test-qofsession "${test_qofsession_SOURCES}"
   gtest_engine_INCLUDES gtest_old_engine_LIBS)
 
 set(test_gnc_int128_SOURCES
   ${MODULEPATH}/gnc-int128.cpp
-  gtest-gnc-int128.cpp
-  ${GTEST_SRC})
+  gtest-gnc-int128.cpp)
 gnc_add_test(test-gnc-int128 "${test_gnc_int128_SOURCES}"
   gtest_engine_INCLUDES gtest_qof_LIBS)
 
@@ -159,8 +155,7 @@ set(test_gnc_rational_SOURCES
   ${MODULEPATH}/qoflog.cpp
   ${CMAKE_SOURCE_DIR}/libgnucash/core-utils/gnc-locale-utils.cpp
   ${gtest_engine_win32_SOURCES}
-  gtest-gnc-rational.cpp
-  ${GTEST_SRC})
+  gtest-gnc-rational.cpp)
 
 gnc_add_test(test-gnc-rational "${test_gnc_rational_SOURCES}"
   gtest_engine_INCLUDES gtest_qof_LIBS)
@@ -175,15 +170,13 @@ set(test_gnc_numeric_SOURCES
   ${MODULEPATH}/qoflog.cpp
   ${CMAKE_SOURCE_DIR}/libgnucash/core-utils/gnc-locale-utils.cpp
   ${gtest_engine_win32_SOURCES}
-  gtest-gnc-numeric.cpp
-  ${GTEST_SRC})
+  gtest-gnc-numeric.cpp)
 gnc_add_test(test-gnc-numeric "${test_gnc_numeric_SOURCES}"
   gtest_engine_INCLUDES gtest_qof_LIBS)
 
 set(test_gnc_timezone_SOURCES
   ${MODULEPATH}/gnc-timezone.cpp
-  gtest-gnc-timezone.cpp
-  ${GTEST_SRC})
+  gtest-gnc-timezone.cpp)
 gnc_add_test(test-gnc-timezone "${test_gnc_timezone_SOURCES}"
   gtest_engine_INCLUDES gtest_old_engine_LIBS)
 
@@ -194,20 +187,17 @@ set(test_gnc_datetime_SOURCES
   ${MODULEPATH}/qoflog.cpp
   ${CMAKE_SOURCE_DIR}/libgnucash/core-utils/gnc-locale-utils.cpp
   ${gtest_engine_win32_SOURCES}
-  gtest-gnc-datetime.cpp
-  ${GTEST_SRC})
+  gtest-gnc-datetime.cpp)
 gnc_add_test(test-gnc-datetime "${test_gnc_datetime_SOURCES}"
   gtest_engine_INCLUDES gtest_qof_LIBS)
 
 set(test_import_map_SOURCES
-  gtest-import-map.cpp
-  ${GTEST_SRC})
+  gtest-import-map.cpp)
 gnc_add_test(test-import-map "${test_import_map_SOURCES}"
   gtest_engine_INCLUDES gtest_old_engine_LIBS)
 
 set(test_qofquerycore_SOURCES
-gtest-qofquerycore.cpp
-${GTEST_SRC})
+gtest-qofquerycore.cpp)
 gnc_add_test(test-qofquerycore "${test_qofquerycore_SOURCES}"
   gtest_engine_INCLUDES gtest_old_engine_LIBS)