Sort the list of sources to be built and linked

Fix reproducibility issue due to readdir() order by sorting
the list of sources to be built and linked.

[jak@debian.org: Added summary and fixed typo]

Closes: #810509

apt-inst/makefile

@@ -20,7 +20,7 @@ SLIBS=$(PTHREADLIB) -lapt-pkg
 APT_DOMAIN:=libapt-inst$(MAJOR)
 LIBRARYDEPENDS=$(LIB)/libapt-pkg.so
 
-SOURCE = $(wildcard *.cc */*.cc)
-HEADERS = $(addprefix apt-pkg/,$(notdir $(wildcard *.h */*.h)))
+SOURCE = $(sort $(wildcard *.cc */*.cc))
+HEADERS = $(addprefix apt-pkg/,$(notdir $(sort $(wildcard *.h */*.h))))
 
 include $(LIBRARY_H)

apt-pkg/makefile

@@ -31,7 +31,7 @@ SLIBS+= -llz4
 endif
 APT_DOMAIN:=libapt-pkg$(LIBAPTPKG_MAJOR)
 
-SOURCE = $(wildcard *.cc */*.cc)
-HEADERS = $(addprefix apt-pkg/,$(notdir $(wildcard *.h */*.h)))
+SOURCE = $(sort $(wildcard *.cc */*.cc))
+HEADERS = $(addprefix apt-pkg/,$(notdir $(sort $(wildcard *.h */*.h))))
 
 include $(LIBRARY_H)

apt-private/makefile

@@ -15,7 +15,7 @@ MINOR=0
 SLIBS=$(PTHREADLIB) -lapt-pkg
 CXXFLAGS += -fvisibility=hidden -fvisibility-inlines-hidden
 
-SOURCE = $(wildcard *.cc)
-HEADERS = $(addprefix apt-private/,$(wildcard *.h))
+SOURCE = $(sort $(wildcard *.cc))
+HEADERS = $(addprefix apt-private/,$(sort $(wildcard *.h)))
 
 include $(LIBRARY_H)