selftests/bpf: Remove unnecessary link dependencies

Remove llvm dependencies from binaries that do not use llvm libraries.
Filter out libxml2 from llvm dependencies, as it seems that
it is not actually used. This patch reduced link dependencies
for BPF selftests.
The next line was adding llvm dependencies to every target in the
makefile, while the only targets that require those are test
runnners (test_progs, test_progs-no_alu32,...):
```
$(OUTPUT)/$(TRUNNER_BINARY): LDLIBS += $$(LLVM_LDLIBS)
```

Before this change:
ldd linux/tools/testing/selftests/bpf/veristat
    linux-vdso.so.1 (0x00007ffd2c3fd000)
    libelf.so.1 => /lib64/libelf.so.1 (0x00007fe1dcf89000)
    libz.so.1 => /lib64/libz.so.1 (0x00007fe1dcf6f000)
    libm.so.6 => /lib64/libm.so.6 (0x00007fe1dce94000)
    libzstd.so.1 => /lib64/libzstd.so.1 (0x00007fe1dcddd000)
    libxml2.so.2 => /lib64/libxml2.so.2 (0x00007fe1dcc54000)
    libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007fe1dca00000)
    libc.so.6 => /lib64/libc.so.6 (0x00007fe1dc600000)
    /lib64/ld-linux-x86-64.so.2 (0x00007fe1dcfb1000)
    liblzma.so.5 => /lib64/liblzma.so.5 (0x00007fe1dc9d4000)
    libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007fe1dcc38000)

After:
ldd linux/tools/testing/selftests/bpf/veristat
    linux-vdso.so.1 (0x00007ffc83370000)
    libelf.so.1 => /lib64/libelf.so.1 (0x00007f4b87515000)
    libz.so.1 => /lib64/libz.so.1 (0x00007f4b874fb000)
    libc.so.6 => /lib64/libc.so.6 (0x00007f4b87200000)
    libzstd.so.1 => /lib64/libzstd.so.1 (0x00007f4b87444000)
    /lib64/ld-linux-x86-64.so.2 (0x00007f4b8753d000)

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250516195522.311769-1-mykyta.yatsenko5@gmail.com

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 0d04cf54068e1605bd40603d627b2f497f233ea6..27db3bf20c21e9ae1e91e62031ba1f03d3c395dd 100644 (file)
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -180,7 +180,7 @@ ifeq ($(feature-llvm),1)
   # Prefer linking statically if it's available, otherwise fallback to shared
   ifeq ($(shell $(LLVM_CONFIG) --link-static --libs >/dev/null 2>&1 && echo static),static)
     LLVM_LDLIBS  += $(shell $(LLVM_CONFIG) --link-static --libs $(LLVM_CONFIG_LIB_COMPONENTS))
-    LLVM_LDLIBS  += $(shell $(LLVM_CONFIG) --link-static --system-libs $(LLVM_CONFIG_LIB_COMPONENTS))
+    LLVM_LDLIBS  += $(filter-out -lxml2,$(shell $(LLVM_CONFIG) --link-static --system-libs $(LLVM_CONFIG_LIB_COMPONENTS)))
     LLVM_LDLIBS  += -lstdc++
   else
     LLVM_LDLIBS  += $(shell $(LLVM_CONFIG) --link-shared --libs $(LLVM_CONFIG_LIB_COMPONENTS))
@@ -675,9 +675,6 @@ ifneq ($2:$(OUTPUT),:$(shell pwd))
        $(Q)rsync -aq $$^ $(TRUNNER_OUTPUT)/
 endif
 
-$(OUTPUT)/$(TRUNNER_BINARY): LDLIBS += $$(LLVM_LDLIBS)
-$(OUTPUT)/$(TRUNNER_BINARY): LDFLAGS += $$(LLVM_LDFLAGS)
-
 # some X.test.o files have runtime dependencies on Y.bpf.o files
 $(OUTPUT)/$(TRUNNER_BINARY): | $(TRUNNER_BPF_OBJS)
 
@@ -688,7 +685,7 @@ $(OUTPUT)/$(TRUNNER_BINARY): $(TRUNNER_TEST_OBJS)                   \
                             $(OUTPUT)/veristat                         \
                             | $(TRUNNER_BINARY)-extras
        $$(call msg,BINARY,,$$@)
-       $(Q)$$(CC) $$(CFLAGS) $$(filter %.a %.o,$$^) $$(LDLIBS) $$(LDFLAGS) -o $$@
+       $(Q)$$(CC) $$(CFLAGS) $$(filter %.a %.o,$$^) $$(LDLIBS) $$(LLVM_LDLIBS) $$(LDFLAGS) $$(LLVM_LDFLAGS) -o $$@
        $(Q)$(RESOLVE_BTFIDS) --btf $(TRUNNER_OUTPUT)/btf_data.bpf.o $$@
        $(Q)ln -sf $(if $2,..,.)/tools/build/bpftool/$(USE_BOOTSTRAP)bpftool \
                   $(OUTPUT)/$(if $2,$2/)bpftool