Add OPENTELEMETRY_INSTALL to allow user to skip install targets.

[owent]

Fixes #2015

Changes

• Add OPENTELEMETRY_INSTALL to allow user to skip install targets.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #2022 (1ae78af) into main (0b72b03) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2022   +/-   ##
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  Coverage   87.32%   87.32%           
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  Files         166      166           
  Lines        4723     4723           
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  Hits         4124     4124           
  Misses        599      599           

[marcalff]

LGTM, thanks for the fix.

[lalitb]

LGTM. Thanks

[dbolduc]

(Maybe this is too late now, but) Do you think this should default to ON in all cases for backwards compatibility?

Do you think the new feature should be listed in INSTALL.md?

opentelemetry-cpp/INSTALL.md

Lines 75 to 86 in f702676

	Some of the available cmake build variables we can use during cmake
	configuration:
	- `-DCMAKE_POSITION_INDEPENDENT_CODE=ON` : Please note that with default
	configuration, the code is compiled without `-fpic` option, so it is not
	suitable for inclusion in shared libraries. To enable the code for
	inclusion in shared libraries, this variable is used.
	- `-DBUILD_SHARED_LIBS=ON` : To build shared libraries for the targets.
	Please refer to note [below](#building-shared-libs-for-windows) for
	Windows DLL support.
	- `-DWITH_OTLP=ON` : To enable building OTLP exporter.
	- `-DWITH_PROMETHEUS=ON` : To enable building prometheus exporter.

[lalitb]

(Maybe this is too late now, but) Do you think this should default to ON in all cases for backwards compatibility?

True, somehow missed this during review. Not sure if reverting back would be good idea as the release is already done now. We can mention this in release summary as breaking change for builds cc @ThomsonTan ?