build: Remove gen/deps.mk

Since commit 3552b79 ("build/flags: Infrastructure to detect compiler
flag support"), this file only listed a bunch of lines like

    -include obj/src/alloc.d
    -include obj/src/bar.d
    ...

We can do that just as well from the main Makefile, and in one line too:

    -include ${OBJS:.o=.d}

This lets us pull the list of all objects out of build/prelude.mk and
put it closer to where those objects are actually used.

Makefile

@@ -50,8 +50,43 @@ BINS := \
 all: ${BINS}
 .PHONY: all
 
+# All object files except the entry point
+LIBBFS := \
+    obj/src/alloc.o \
+    obj/src/bar.o \
+    obj/src/bfstd.o \
+    obj/src/bftw.o \
+    obj/src/color.o \
+    obj/src/ctx.o \
+    obj/src/diag.o \
+    obj/src/dir.o \
+    obj/src/dstring.o \
+    obj/src/eval.o \
+    obj/src/exec.o \
+    obj/src/expr.o \
+    obj/src/fsade.o \
+    obj/src/ioq.o \
+    obj/src/mtab.o \
+    obj/src/opt.o \
+    obj/src/parse.o \
+    obj/src/printf.o \
+    obj/src/pwcache.o \
+    obj/src/sighook.o \
+    obj/src/stat.o \
+    obj/src/thread.o \
+    obj/src/trie.o \
+    obj/src/typo.o \
+    obj/src/version.o \
+    obj/src/xregex.o \
+    obj/src/xspawn.o \
+    obj/src/xtime.o
+
+# All object files
+OBJS := ${LIBBFS}
+
 # The main binary
-bin/bfs: ${LIBBFS} obj/src/main.o
+bin/bfs: obj/src/main.o ${LIBBFS}
+OBJS += obj/src/main.o
 
 ${BINS}:
 	@${MKDIR} ${@D}
@@ -61,11 +96,6 @@ ${BINS}:
 # Get the .c file for a .o file
 CSRC = ${@:obj/%.o=%.c}
 
-# Rebuild when the configuration changes
-${OBJS}: gen/config.mk
-	@${MKDIR} ${@D}
-	${MSG} "[ CC ] ${CSRC}" ${CC} ${_CPPFLAGS} ${_CFLAGS} -c ${CSRC} -o $@
-
 # Save the version number to this file, but only update version.c if it changes
 gen/version.i.new::
 	${MKDIR} ${@D}
@@ -103,12 +133,24 @@ unit-tests: ${UTEST_BINS}
 	${MSG} "[TEST] tests/units" bin/tests/units
 .PHONY: unit-tests
 
-bin/tests/units: \
-    ${UNIT_OBJS} \
-    ${LIBBFS}
-
-bin/tests/xspawnee: \
-    obj/tests/xspawnee.o
+# Unit test objects
+UNIT_OBJS := \
+    obj/tests/alloc.o \
+    obj/tests/bfstd.o \
+    obj/tests/bit.o \
+    obj/tests/ioq.o \
+    obj/tests/list.o \
+    obj/tests/main.o \
+    obj/tests/sighook.o \
+    obj/tests/trie.o \
+    obj/tests/xspawn.o \
+    obj/tests/xtime.o
+
+bin/tests/units: ${UNIT_OBJS} ${LIBBFS}
+OBJS += ${UNIT_OBJS}
+
+bin/tests/xspawnee: obj/tests/xspawnee.o
+OBJS += obj/tests/xspawnee.o
 
 # The different flag combinations we check
 INTEGRATIONS := default dfs ids eds j1 j2 j3 s
@@ -133,13 +175,11 @@ check-j1 check-j2 check-j3 check-s: bin/bfs ${ITEST_BINS}
 integration-tests: ${INTEGRATION_TESTS}
 .PHONY: integration-tests
 
-bin/tests/mksock: \
-    obj/tests/mksock.o \
-    ${LIBBFS}
+bin/tests/mksock: obj/tests/mksock.o ${LIBBFS}
+OBJS += obj/tests/mksock.o
 
-bin/tests/xtouch: \
-    obj/tests/xtouch.o \
-    ${LIBBFS}
+bin/tests/xtouch: obj/tests/xtouch.o ${LIBBFS}
+OBJS += obj/tests/xtouch.o
 
 # `make distcheck` configurations
 DISTCHECKS := \
@@ -173,6 +213,16 @@ ${DISTCHECKS}::
 	    && ../configure MAKE="${MAKE}" ${DISTCHECK_CONFIG_${@:distcheck-%=%}} \
 	    && ${MAKE} check TEST_FLAGS="--sudo --verbose=skipped"
 
+## Automatic dependency tracking
+
+# Rebuild when the configuration changes
+${OBJS}: gen/config.mk
+	@${MKDIR} ${@D}
+	${MSG} "[ CC ] ${CSRC}" ${CC} ${_CPPFLAGS} ${_CFLAGS} -c ${CSRC} -o $@
+
+# Include any generated dependency files
+-include ${OBJS:.o=.d}
+
 ## Packaging (`make install`)
 
 DEST_PREFIX := ${DESTDIR}${PREFIX}

build/config.mk

@@ -14,7 +14,6 @@ config: gen/config.mk
 MKS := \
     gen/vars.mk \
     gen/flags.mk \
-    gen/deps.mk \
     gen/pkgs.mk
 
 # The main configuration file, which includes the others
@@ -47,11 +46,6 @@ gen/flags.mk: gen/vars.mk
 	@+XMAKEFLAGS="$$MAKEFLAGS" ${MAKE} -sf build/flags.mk $@
 .PHONY: gen/flags.mk
 
-# Check for dependency generation support
-gen/deps.mk: gen/flags.mk
-	@+XMAKEFLAGS="$$MAKEFLAGS" ${MAKE} -sf build/deps.mk $@
-.PHONY: gen/deps.mk
-
 # Auto-detect dependencies and their build flags
 gen/pkgs.mk: gen/flags.mk
 	@+XMAKEFLAGS="$$MAKEFLAGS" ${MAKE} -sf build/pkgs.mk $@

build/header.mk

@@ -6,7 +6,6 @@
 include build/prelude.mk
 include gen/vars.mk
 include gen/flags.mk
-include gen/deps.mk
 include gen/pkgs.mk
 include build/exports.mk
 

build/prelude.mk

@@ -71,50 +71,6 @@ ALL_PKGS := \
 
 # List all object files here, as they're needed by both `./configure` and `make`
 
-# All object files except the entry point
-LIBBFS := \
-    obj/src/alloc.o \
-    obj/src/bar.o \
-    obj/src/bfstd.o \
-    obj/src/bftw.o \
-    obj/src/color.o \
-    obj/src/ctx.o \
-    obj/src/diag.o \
-    obj/src/dir.o \
-    obj/src/dstring.o \
-    obj/src/eval.o \
-    obj/src/exec.o \
-    obj/src/expr.o \
-    obj/src/fsade.o \
-    obj/src/ioq.o \
-    obj/src/mtab.o \
-    obj/src/opt.o \
-    obj/src/parse.o \
-    obj/src/printf.o \
-    obj/src/pwcache.o \
-    obj/src/sighook.o \
-    obj/src/stat.o \
-    obj/src/thread.o \
-    obj/src/trie.o \
-    obj/src/typo.o \
-    obj/src/version.o \
-    obj/src/xregex.o \
-    obj/src/xspawn.o \
-    obj/src/xtime.o \
-
-# Unit test objects
-UNIT_OBJS := \
-    obj/tests/alloc.o \
-    obj/tests/bfstd.o \
-    obj/tests/bit.o \
-    obj/tests/ioq.o \
-    obj/tests/list.o \
-    obj/tests/main.o \
-    obj/tests/sighook.o \
-    obj/tests/trie.o \
-    obj/tests/xspawn.o \
-    obj/tests/xtime.o
-
 # All object files
 OBJS := \
     obj/src/main.o \