无法配置空间，因为它无法检测到 PROJ (libproj)

这里有同样的问题，有这条消息：

configure: error: 'libproj' is required but it doesn't seem to be installed on this system.

解决方法：

apt-get update && apt-get -y install libproj-dev

连同：

apt-get -y install build-essential pkg-config \
  libfreexl-dev  \
  libgeos-dev  \
  librttopo-dev  \
  libxml2  \
  libzip-dev  \
  libminizip-dev

./configure

.
..
...
....

==============================================================
                        IMPORTANT NOTICE
==============================================================
You have SELEcted --enable-rttopo and/or --enable-gcp

Both modules Strictly depend on code released under the GPLv2+
license,wich takes precedence over any other license.
Consequently the copy of libspatialite you are going to build
if configured this way *must* be released under the GPLv2+ license.

If you wish better preserving the initial MPL tri-license you
simply have to reconfigure by specifying the following options:
        --disable-rttopo --disable-gcp
==============================================================

测试：

# cat /etc/lsb-release 
DIStriB_ID=Ubuntu
DIStriB_RELEASE=20.04
DIStriB_CODename=focal
DIStriB_DESCRIPTION="Ubuntu 20.04.1 LTS"

# uname -mor
5.4.0-65-generic x86_64 GNU/Linux

# gcc --version
gcc (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0
Copyright (C) 2019 Free Software Foundation,Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITnesS FOR A PARTICULAR PURPOSE.