[ELF] -r: force -Bstatic

In GNU ld, -r forces -Bstatic and has precedence over -Bdynamic: -lfoo
probes libfoo.a but not libfoo.so, even if -Bdynamic is in effect. Our
behavior currently matches gold and probes libfoo.so. Since we don't
have strong opinion on the exact behavior, let's just follow GNU ld and
also unify the reason we report the "attempted static link of dynamic
object " error.

Close #94958

lld/ELF/Driver.cpp

@@ -324,7 +324,7 @@ void LinkerDriver::addFile(StringRef path, bool withLOption) {
     return;
   }
   case file_magic::elf_shared_object: {
-    if (config->isStatic || config->relocatable) {
+    if (config->isStatic) {
       error("attempted static link of dynamic object " + path);
       return;
     }
@@ -1892,6 +1892,9 @@ void LinkerDriver::createFiles(opt::InputArgList &args) {
   // For --{push,pop}-state.
   std::vector<std::tuple<bool, bool, bool>> stack;
 
+  // -r implies -Bstatic and has precedence over -Bdynamic.
+  config->isStatic = config->relocatable;
+
   // Iterate over argv to process input files and positional arguments.
   std::optional<MemoryBufferRef> defaultScript;
   InputFile::isInGroup = false;
@@ -1946,7 +1949,8 @@ void LinkerDriver::createFiles(opt::InputArgList &args) {
       config->isStatic = true;
       break;
     case OPT_Bdynamic:
-      config->isStatic = false;
+      if (!config->relocatable)
+        config->isStatic = false;
       break;
     case OPT_whole_archive:
       inWholeArchive = true;

lld/test/ELF/libsearch.s

@@ -91,6 +91,12 @@
 // RUN: ld.lld -o %t3 %t.o -L%t.dir -Bstatic -call_shared -lls
 // RUN: llvm-readobj --symbols %t3 | FileCheck --check-prefix=DYNAMIC %s
 
+/// -r implies -Bstatic and has precedence over -Bdynamic.
+// RUN: ld.lld -r -Bdynamic %t.o -L%t.dir -lls -o %t3.ro
+// RUN: llvm-readelf -s -h %t3.ro | FileCheck --check-prefix=RELOCATABLE %s
+// RELOCATABLE: Type: REL
+// RELOCATABLE: [[#]] _static
+
 // -nostdlib
 // RUN: echo 'SEARCH_DIR("'%t.dir'")' > %t.script
 // RUN: ld.lld -o %t3 %t.o -script %t.script -lls