gnu: Disable parallel tests.

* gnu/packages/aidc.scm (zint),
* gnu/packages/calendar.scm (libical),
* gnu/packages/compression.scm (c-blosc2, minizip-ng),
* gnu/packages/cpp.scm (cpp-httplib),
* gnu/packages/engineering.scm (libmedfile),
* gnu/packages/gnome.scm (evolution-data-server),
* gnu/packages/image-processing.scm (opencv),
* gnu/packages/kde-frameworks.scm (kservice),
* gnu/packages/maths.scm (scotch),
* gnu/packages/networking.scm (restbed, restinio, srt),
* gnu/packages/tbb.scm (tbb),
* gnu/packages/tls.scm (mbedtls-lts),
* gnu/packages/vulkan.scm (vulkan-loader),
* gnu/packages/web.scm (websocketpp)
[arguments]<#:parallel-tests?>: Disable.

Change-Id: I88334deb4afc29ab84b279e9d1759a777ddd49dd

gnu/packages/cpp.scm

@@ -1649,7 +1649,8 @@ tools:
        (file-name (git-file-name name version))))
     (build-system cmake-build-system)
     (arguments
-     `(#:configure-flags
+     `(#:parallel-tests? #f
+       #:configure-flags
        '("-DBUILD_SHARED_LIBS=ON"
          "-DHTTPLIB_TEST=ON"
          "-DHTTPLIB_COMPILE=ON"