Travis CI: Make lld the default linker

As for Azure CI Linux, using the LLD bundled with the LDC-LLVM
package and thus matching the LLVM version LDC is linked against.

The prebuilt Linux packages are thus linked with LLD now.

Author: kinke

.azure-pipelines/1-posix-setup.yml

@@ -63,7 +63,7 @@ steps:
     fi
     mkdir llvm
     tar -xf llvm.tar.xz --strip 1 -C llvm
-    # Non-Mac: make lld the default linker
+    # Non-Mac: make lld the default linker (possibly with enabled assertions unfortunately)
     if [ "$CI_OS" != "osx" ]; then
       sudo ln -sf "$PWD/llvm/bin/ld.lld" /usr/bin/ld
     fi

.travis.yml

@@ -9,7 +9,8 @@ env:
     - LLVM_VERSION=12.0.0
     - CC=gcc-8
     - CXX=g++-8
-    - OPTS="-DBUILD_LTO_LIBS=ON -DCMAKE_EXE_LINKER_FLAGS=-static-libstdc++ -DJITRT_EXTRA_LDFLAGS=-static-libstdc++ -DLDC_INSTALL_LLVM_RUNTIME_LIBS_ARCH=aarch64"
+    # FIXME: need to use ld.gold for linking LDC itself for now, fixed in frontend v2.099
+    - OPTS="-DBUILD_LTO_LIBS=ON -DCMAKE_EXE_LINKER_FLAGS=-static-libstdc++ -DJITRT_EXTRA_LDFLAGS=-static-libstdc++ -DD_COMPILER_FLAGS=-linker=gold -DLDC_INSTALL_LLVM_RUNTIME_LIBS_ARCH=aarch64"
     - secure: "WfMv0kOqVU8+SgZUrwgzvzGvFbZvPmeIqrDJ+sotbzEtDeCcMuZmj/+8VuysXzpShXx/FxCoopWpAz30pedES8anGR3ciZruVPPsi22rOR5IBHuSnbamkmF11eQgRaDcj6GvZL7QeWLHBx6EN+C+mQFEVqRrD5avCO/K0RqWTD4="
 
 git:
@@ -46,6 +47,8 @@ install:
     mkdir -p llvm || travis_terminate 1
     tar -xf llvm.tar.xz --strip 1 -C llvm || travis_terminate 1
     rm llvm.tar.xz || travis_terminate 1
+  # Make lld the default linker (possibly with enabled assertions unfortunately)
+  - sudo ln -sf "$PWD/llvm/bin/ld.lld" /usr/bin/ld
 
 script:
   - unset LD_LIBRARY_PATH
@@ -134,9 +137,9 @@ script:
   - installed/bin/ldc2 hello.d -of=hello -link-defaultlib-shared
   - ./hello
   # Run hello-world integration test with LTO
-  - installed/bin/ldc2 hello.d -of=hello_thin -linker=gold -flto=thin -defaultlib=phobos2-ldc-lto,druntime-ldc-lto
+  - installed/bin/ldc2 hello.d -of=hello_thin -flto=thin -defaultlib=phobos2-ldc-lto,druntime-ldc-lto
   - ./hello_thin
-  - installed/bin/ldc2 hello.d -of=hello_full -linker=gold -flto=full -defaultlib=phobos2-ldc-lto,druntime-ldc-lto
+  - installed/bin/ldc2 hello.d -of=hello_full -flto=full -defaultlib=phobos2-ldc-lto,druntime-ldc-lto
   - ./hello_full
   # Run dynamic-compile integration test
   # FIXME: disabled since LLVM 12, needs https://github.com/ldc-developers/ldc/pull/3184