Merge topic 'fix-GEH-docs'

0ebf332 Fix GenerateExportHeader documentation #13936
Merge topic 'generate-export-header-warnings'

1e0891e Removed GenerateExportHeader warnings about old compilers
Merge topic 'cmLocalGenerator_RemoveVirtuals'

f497dbc cmLocalGenerator: remove "virtual" where not used
Merge topic 'ExportFileGenerator_GenerateNicerErrorCheckingCode'

11d0c66 export files: rewrite the code for checking required targets
Merge topic 'ExternalData-spaces'

55f0148 ExternalData: Test content link with a space in its name
d45eb35 Tests: Generalize decision for 'make' tool supporting spaces
ef8b2fd Tests: Replace exec_program with execute_process
Merge topic 'fix-automoc-linker-language'

79568f9 automoc: Add source file to target early to set the linker language
Merge topic 'try_compile-targets'

236133e Handle targets in the LINK_LIBRARIES of try_compile.
1c0597c Add a new Export generator for IMPORTED targets.
f2ab17d Keep track of all targets seen while evaluating a genex.
Merge topic 'FPHSA_FOUND_VAR_OPTION'

f17711c FPHSA: Convert FOUND_VAR failure test to RunCMake
c1f5780 FPHSA: improve documentation
7bb1abe FPHSA: Add FOUND_VAR option to specify _FOUND variable name
Merge topic 'ide-compiler-vars-Fortran'

9f94181 VS: Restore CMAKE_GENERATOR_FC variable
Merge topic 'interface-property-external-read'

8dfdf1c Fix the tests for evaluating includes and defines.
98a6725 Fix constness of accessors.
7e70744 Expand includes and defines transitively in 'external' genexes.
d1a2729 Fix DAG checker finding cycling dependencies.
e72eaad Workaround broken code where a target has itself in its link iface.
ec2c67b Strip stray semicolons when evaluating generator expressions.
Merge topic 'memoize-link-iface-includes-defines'

42ebb18 Memoize includes and defines from interface libraries.
Merge branch 'master' into next