fix(#1947): report errors for FindwxWidgets.cmake

[slodki]

Diagnose #1947 under Unix

When wxWidgets are not found:

Could NOT find wxWidgets (missing: wxWidgets_LIBRARIES
wxWidgets_INCLUDE_DIRS) (Required is at least version "2.9.2")

wxWidgets with some components missing:

Could NOT find wxWidgets (missing: webview) (found suitable version
"3.1.2", minimum required is "2.9.2")

wxWidgets found with all required components (optional components can be missing):

Found wxWidgets: -L/usr/lib/x86_64-linux-gnu;-pthread;;;-lwx_gtk3u_unofficial3_core-3.1;-lwx_gtk3u_unofficial3_qa-3.1;-lwx_gtk3u_unofficial3_html-3.1;-lwx_baseu_unofficial3_xml-3.1;-lwx_gtk3u_unofficial3_aui-3.1;-lwx_gtk3u_unofficial3_stc-3.1;-lwx_gtk3u_unofficial3_webview-3.1;-lwx_baseu_unofficial3-3.1 (found suitable version "3.1.2", minimum required is "2.9.2") found components: core qa html xml aui adv stc webview base missing components: scintilla

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