Buildkite: Fix regression with LDC v1.41.0 (#492)

Old workarounds getting in the way apparently, faking a cross-compilation
scenario, where LDC v1.41 newly doesn't include the druntime/Phobos libraries
by default anymore.

Author: kinke

buildkite/build_project.sh

@@ -273,19 +273,14 @@ case "$REPO_FULL_NAME" in
         cmake .. \
           -GNinja \
           -DCMAKE_BUILD_TYPE=Debug \
-          -DD_COMPILER="$DC" \
-          -DCMAKE_SYSTEM_NAME=Linux # work around gen_gccbuiltins linker issue with llvm-8 pkg
+          -DD_COMPILER="$DC"
         ninja -j2 ldmd2 druntime-ldc-debug phobos2-ldc-debug
         cd ..
         mkdir build && cd build
-        # LDC_LINK_MANUALLY=OFF works around an LDC 1.24.0 problem with CMAKE_BUILD_TYPE=Debug
-        # without *release* host druntime/Phobos.
         cmake .. \
           -GNinja \
           -DCMAKE_BUILD_TYPE=Debug \
-          -DD_COMPILER="$(pwd)/../bootstrap/bin/ldmd2" \
-          -DLDC_LINK_MANUALLY=OFF \
-          -DCMAKE_SYSTEM_NAME=Linux # work around gen_gccbuiltins linker issue with llvm-8 pkg
+          -DD_COMPILER="$(pwd)/../bootstrap/bin/ldmd2"
         ninja -j2 ldc2 druntime-ldc phobos2-ldc
         ;;