Bug#1127799: libdeal.ii-dev must depend on mold where it was used for building

[Adrian Bunk]

Package: libdeal.ii-dev
Version: 9.7.1-3
Severity: serious
Control: affects -1 src:deal.ii

https://ci.debian.net/packages/d/deal.ii/testing/amd64/68661830/

...
106s [ 66%] Linking CXX executable step-1
106s collect2: fatal error: cannot find ‘ld’
106s compilation terminated.
106s make[3]: *** [CMakeFiles/step-1.dir/build.make:460: step-1] Error 1
106s make[2]: *** [CMakeFiles/Makefile2:94: CMakeFiles/step-1.dir/all] Error 2
106s make[1]: *** [CMakeFiles/Makefile2:133: CMakeFiles/run.dir/rule] Error 2
106s make: *** [Makefile:137: run] Error 2
106s autopkgtest [03:38:34]: test smoke-test: -----------------------]
106s autopkgtest [03:38:34]: test smoke-test:  - - - - - - - - - - results - - - - - - - - - -
106s smoke-test           FAIL non-zero exit status 2
...


Due to:
/usr/share/cmake/deal.II/deal.IIConfig.cmake:set(DEAL_II_LINKER_FLAGS "-rdynamic -fuse-ld=mold -Wl,-z,relro")
/usr/share/cmake/deal.II/deal.IITargets.cmake:  INTERFACE_LINK_OPTIONS "-rdynamic;-fuse-ld=mold;-Wl,-z,relro;\$<\$<CONFIG:Debug>:-ggdb;-Wl,--compress-debug-sections=zlib>;\$<\$<CONFIG:Release>:>"