cherry-picking commit 4d5be00 from @cottsay
See: wjwwood#209 (comment)

 Author:    Scott K Logan <[email protected]>
 Date:      Wed Jul 3 13:24:15 2019 -0700

Conflicts:
	CMakeLists.txt
	package.xml
	tests/CMakeLists.txt

Signed-off-by: Alex Moriarty <[email protected]>

This couldn't be cherry-picked because but essentially the same change
from the ros2 branch here:
tylerjw@d8d1606

Fixes this error:

```
/usr/bin/ld: /home/alex/ros/h/robotiq/install/serial/lib/libserial.a(serial.cc.o): relocation R_X86_64_PC32 against symbol `_ZTVN6serial6SerialE' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: bad value
```

Signed-off-by: Alex Moriarty <[email protected]>

Cmake made major changes in the 2.x -> 3.0 switch, keeping the 2.x
compatiblity just isn't worth it. Since serial anyway doesn't build on
versions before xenial, use xenial's cmake at 3.5 as baseline.

Cherry-pick from PR wjwwood#231

 Conflicts:
	CMakeLists.txt
 Author:    Alec Leamas <[email protected]>
 Date:      Tue Sep 22 13:08:46 2020 +0200

Gbp-Pq: Name 0001-cmake-Use-cmake-3.5-add-project-setup.patch
Signed-off-by: Alex Moriarty <[email protected]>

Adding a so-version means defining an ABI level. This level is decoupled
from the ordinary version, even a major version change doesn't
necessarily mean that the so-version should change (and thus have all
dependencies to be rebuilt).

Adding the public header to clarify the setup.

Note: cherry-pick from PR wjwwood#231

 Conflicts:
	CMakeLists.txt
 Author:    Alec Leamas <[email protected]>
 Date:      Tue Sep 22 13:28:04 2020 +0200

Gbp-Pq: Name 0002-cmake-Add-defined-so-version-and-public-header-to-li.patch
Signed-off-by: Alex Moriarty <[email protected]>

Default to building as a shared libary

Signed-off-by: Alex Moriarty <[email protected]>

- remove set BUILD_SHARED_LIBS ON
- set CMAKE_POSITION_INDEPENDENT_CODE ON if undefined

When setting BUILD_SHARED_LIBS if user set it to off linking would fail.
Adding the suggetion from pull request review, which seems to work in
both cases

    colcon build --cmake-args "-DBUILD_SHARED_LIBS=ON"
    colcon build --cmake-args "-DBUILD_SHARED_LIBS=OFF"

Signed-off-by: Alex Moriarty <[email protected]>

Bump cmake to oldest version currently used by tier 1 or 2 supported ROS
platform.

https://www.ros.org/reps/rep-2000.html#humble-hawksbill-may-2022-may-2027
https://www.ros.org/reps/rep-0003.html#noetic-ninjemys-may-2020-may-2025

Signed-off-by: Alex Moriarty <[email protected]>

this is only used once and it makes it easier to read or grep for

Signed-off-by: Alex Moriarty <[email protected]>

Co-authored-by: Chris Thrasher <[email protected]>

- Find and use GTest as imported target GTest::GTest
- Note:
  - GTest::GTest is available from CMake 3.5 and depricated in 3.20 but
    still available in latest version.
  - GTest::gtest added in CMake 3.20

Signed-off-by: Alex Moriarty <[email protected]>