gnu: Use the CMake build system's #:build-type key.

gnu: Use the CMake build system's #:build-type key.

* gnu/packages/code.scm (rtags)[arguments]: Move the CMAKE_BUILD_TYPE
from #:configure-flags to #:build-type.
* gnu/packages/databases.scm (apache-arrow)[arguments]: Likewise
* gnu/packages/engineering.scm (kicad)[arguments]: Likewise
* gnu/packages/flashing-tools.scm (heimdall)[arguments]: Likewise
* gnu/packages/graphics.scm (openscenegraph)[arguments]: Likewise
* gnu/packages/linux.scm (rdma-core)[arguments]: Likewise
* gnu/packages/music.scm (portmidi)[arguments]: Likewise
* gnu/packages/photo.scm (rawtherapee)[arguments]: Likewise
* gnu/packages/rdesktop.scm (freerdp)[arguments]: Likewise
* gnu/packages/serialization.scm (flatbuffers)[arguments]: Likewise
* gnu/packages/web.scm (tidy-html)[arguments]: Likewise