mirror: Define PACKAGE at build time when trying to detect libbfd

Feature detection from the Makefile.feature for libbfd (with the
different variants of the probe) may fail on some systems where the
bfd.h and dis-asm.h headers expect the PACKAGE or PACKAGE_VERSION macros
to be defined [0]. In the kernel tree, feature detection addresses it by
defining the PACKAGE macro when invoking the compiler [1]. Add a similar
definition for the mirror repository.

Note that this issue has remained undetected for a while. This is
because the bfd.h included in some distributions (Debian/Ubuntu, for
example) does not contain the inclusion guard [2].

[0] https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=bfd/bfd-in.h;h=04e65aad5f0c235a5013513c545e57a01e96541f;hb=binutils-2_43_1#l27
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/build/feature/Makefile?h=v6.11#n114
[2] https://git.launchpad.net/ubuntu/+source/binutils/tree/debian/rules?h=applied/2.43.1-5#n1031

Reported-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Signed-off-by: Quentin Monnet <qmo@kernel.org>

src/Makefile.feature

@@ -45,7 +45,7 @@ LIBBFD_PROBE += '	bfd_demangle(0, 0, 0);'
 LIBBFD_PROBE += '	return 0;'
 LIBBFD_PROBE += '}'
 LIBBFD_PROBE_CMD = printf '%b\n' $(LIBBFD_PROBE) | \
-  $(CC) $(CFLAGS) -Wall -Werror -x c - $(1) -o /dev/null >/dev/null
+  $(CC) $(CFLAGS) -Wall -Werror -x c -DPACKAGE='"bpftool"' - $(1) -o /dev/null >/dev/null
 
 define libbfd_build
   $(call detect,$(LIBBFD_PROBE_CMD))
@@ -78,7 +78,7 @@ DISASSEMBLER_PROBE += '	return 0;'
 DISASSEMBLER_PROBE += '}'
 
 DISASSEMBLER_PROBE_CMD = printf '%b\n' $(1) | \
-  $(CC) $(CFLAGS) -Wall -Werror -x c - -lbfd -lopcodes -S -o - >/dev/null
+  $(CC) $(CFLAGS) -Wall -Werror -x c -DPACKAGE='"bpftool"' - -lbfd -lopcodes -S -o - >/dev/null
 define disassembler_build
   $(call detect,$(DISASSEMBLER_PROBE_CMD))
 endef