refactor building system of cmake by this project, first try from linux

.gitignore

@@ -1,174 +1,4 @@
-*build/
-compile_commands.json
-CMakeSettings.json
-.cache
-.ycm_extra_conf.py
-.tasks
-.vimspector.json
-.vscode/
-.vscode
-.idea/
-cmake-build-debug/
-cmake-build-release/
-cscope.out
-cscope.files
-.DS_Store
+.externals/
 debug/
-release/
-target/
-debs/
-rpms/
-mac/
-*.pyc
-.mypy_cache
-*.tmp
 *.swp
-*.swo
-*.orig
-src/connector/nodejs/node_modules/
-src/connector/nodejs/out/
-tests/taoshebei/
-tests/taoscsv/
-tests/taosdalipu/
-tests/jenkins/
-tests/hdfs/
-*.iml
-*.class
-nmake/
-sln/
-hdfs/
-taoshebei/
-taosdalipu/
-Target/
-*.failed
-*.sql
-sim
-sim/
-psim/
-pysim/
-*.out
-*DS_Store
-tests/script/api/batchprepare
-taosadapter
-taosadapter-debug
-tools/taos-tools/*
-tools/taosws-rs/*
-tools/taosadapter/*
-tools/upx*
 
-# Doxygen Generated files
-html/
-/.vs
-/CMakeFiles/3.10.2
-/CMakeCache.txt
-/Makefile
-/*.cmake
-/src/cq/test/CMakeFiles/cqtest.dir/*.cmake
-*.cmake
-/src/cq/test/CMakeFiles/cqtest.dir/*.make
-*.make
-link.txt
-*.internal
-*.includecache
-*.marks
-Makefile
-CMakeError.log
-*.log
-/CMakeFiles/CMakeRuleHashes.txt
-/CMakeFiles/Makefile2
-/CMakeFiles/TargetDirectories.txt
-/CMakeFiles/cmake.check_cache
-/out/isenseconfig/WSL-Clang-Debug
-/out/isenseconfig/WSL-GCC-Debug
-/test/cfg
-/src/.vs
-*.o
-version.c
-taos.rc
-src/connector/jdbc/.classpath
-src/connector/jdbc/.project
-src/connector/jdbc/.settings/
-tests/comparisonTest/cassandra/cassandratest/.classpath
-tests/comparisonTest/cassandra/cassandratest/.project
-tests/comparisonTest/cassandra/cassandratest/.settings/
-tests/comparisonTest/opentsdb/opentsdbtest/.classpath
-tests/comparisonTest/opentsdb/opentsdbtest/.factorypath
-tests/comparisonTest/opentsdb/opentsdbtest/.project
-tests/comparisonTest/opentsdb/opentsdbtest/.settings/
-tests/examples/JDBC/JDBCDemo/.classpath
-tests/examples/JDBC/JDBCDemo/.project
-tests/examples/JDBC/JDBCDemo/.settings/
-source/libs/parser/inc/sql.*
-source/os/src/timezone/
-tests/script/tmqResult.txt
-tests/system-test/case_to_run.txt
-tests/develop-test/case_to_run.txt
-tests/scripts/case_to_run.txt
-tests/tmqResult.txt
-tests/script/jenkins/basic.txt
-
-# Emacs
-# -*- mode: gitignore; -*-
-*~
-\#*\#
-/.emacs.desktop
-/.emacs.desktop.lock
-*.elc
-auto-save-list
-tramp
-.\#*
-TAGS
-
-contrib/*
-!contrib/CMakeLists.txt
-!contrib/test
-!contrib/azure-cmake
-sql
-debug*/
-.env
-tools/README
-tools/LICENSE
-tools/README.1ST
-tools/THANKS
-tools/NEWS
-tools/COPYING
-tools/BUGS
-tools/taos-tools
-tools/taosws-rs
-tags
-.clangd
-*CMakeCache*
-*CMakeFiles*
-.history/
-*.txt
-*.tcl
-*.pc
-contrib/geos
-contrib/libuv
-contrib/pcre2
-contrib/zlib
-deps_tmp_CMakeLists.txt.in
-*.a
-*.ctest
-pcre2-config
-pcre2_test.sh
-pcre2_grep_test.sh
-pcre2_chartables.c
-geos-config
-config.h
-pcre2.h
-zconf.h
-version.h
-geos_c.h
-source/libs/parser/src/sql.c
-include/common/ttokenauto.h
-!packaging/smokeTest/pytest_require.txt
-tdengine-test-dir/
-localtime.c
-private.h
-strftime.c
-tzdir.h
-tzfile.h
-coverage.info
-taos
-taosd

CMakeLists.txt

@@ -6,6 +6,18 @@ project(
   DESCRIPTION "An open-source big data platform designed and optimized for the Internet of Things(IOT)"
 )
 
+option(FALLBACK "fall back to original"     OFF)
+
+if(NOT ${FALLBACK})        # {
+    set(TD_EXTERNALS              ${CMAKE_SOURCE_DIR}/.externals)
+    macro(init_external name)
+      set(_base           "${TD_EXTERNALS}/${name}")
+      set(_ins            "${TD_EXTERNALS}/${name}/install")
+      set(${name}_base    "${_base}"          PARENT_SCOPE)
+      set(${name}_install "${_ins}"           PARENT_SCOPE)
+    endmacro()
+endif()                    # }
+
 if(NOT DEFINED TD_SOURCE_DIR)
   set(TD_SOURCE_DIR ${PROJECT_SOURCE_DIR})
 endif()