diff --git a/core/clang/config.mk b/core/clang/config.mk
index 6887522..cd91c6c 100644
--- a/core/clang/config.mk
+++ b/core/clang/config.mk
@@ -78,7 +78,8 @@
   -Wno-unused-local-typedefs \
   -Wunused-but-set-parameter \
   -Wunused-but-set-variable \
-  -fdiagnostics-color
+  -fdiagnostics-color \
+  -fdebug-prefix-map=/proc/self/cwd=
 
 # Clang flags for all host rules
 CLANG_CONFIG_HOST_EXTRA_ASFLAGS :=
diff --git a/core/config.mk b/core/config.mk
index 1db3d7a..2a16680 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -177,6 +177,19 @@
 FIND_LEAVES_EXCLUDES := $(addprefix --prune=, $(OUT_DIR) $(SCAN_EXCLUDE_DIRS) .repo .git)
 
 # ---------------------------------------------------------------
+# We run gcc/clang with PWD=/proc/self/cwd to remove the $TOP
+# from the debug output. That way two builds in two different
+# directories will create the same output.
+# /proc doesn't exist on Darwin.
+ifeq ($(HOST_OS),linux)
+RELATIVE_PWD := PWD=/proc/self/cwd
+# Remove this useless prefix from the debug output.
+COMMON_GLOBAL_CFLAGS += -fdebug-prefix-map=/proc/self/cwd=
+else
+RELATIVE_PWD :=
+endif
+
+# ---------------------------------------------------------------
 # Allow the C/C++ macros __DATE__ and __TIME__ to be set to the
 # build date and time, so that a build may be repeated.
 # Write the date and time to a file so that the command line
diff --git a/core/definitions.mk b/core/definitions.mk
index c179706..3d9b301 100644
--- a/core/definitions.mk
+++ b/core/definitions.mk
@@ -1049,7 +1049,7 @@
 define transform-cpp-to-o
 @echo "target $(PRIVATE_ARM_MODE) C++: $(PRIVATE_MODULE) <= $<"
 @mkdir -p $(dir $@)
-$(hide) $(PRIVATE_CXX) \
+$(hide) $(RELATIVE_PWD) $(PRIVATE_CXX) \
 	$(addprefix -I , $(PRIVATE_C_INCLUDES)) \
 	$(shell cat $(PRIVATE_IMPORT_INCLUDES)) \
 	$(addprefix -isystem ,\
@@ -1081,7 +1081,7 @@
 # $(1): extra flags
 define transform-c-or-s-to-o-no-deps
 @mkdir -p $(dir $@)
-$(hide) $(PRIVATE_CC) \
+$(hide) $(RELATIVE_PWD) $(PRIVATE_CC) \
 	$(addprefix -I , $(PRIVATE_C_INCLUDES)) \
 	$(shell cat $(PRIVATE_IMPORT_INCLUDES)) \
 	$(addprefix -isystem ,\
@@ -1156,7 +1156,7 @@
 define transform-host-cpp-to-o
 @echo "$($(PRIVATE_PREFIX)DISPLAY) C++: $(PRIVATE_MODULE) <= $<"
 @mkdir -p $(dir $@)
-$(hide) $(PRIVATE_CXX) \
+$(hide) $(RELATIVE_PWD) $(PRIVATE_CXX) \
 	$(addprefix -I , $(PRIVATE_C_INCLUDES)) \
 	$(shell cat $(PRIVATE_IMPORT_INCLUDES)) \
 	$(addprefix -isystem ,\
@@ -1186,7 +1186,7 @@
 # $(1): extra flags
 define transform-host-c-or-s-to-o-no-deps
 @mkdir -p $(dir $@)
-$(hide) $(PRIVATE_CC) \
+$(hide) $(RELATIVE_PWD) $(PRIVATE_CC) \
 	$(addprefix -I , $(PRIVATE_C_INCLUDES)) \
 	$(shell cat $(PRIVATE_IMPORT_INCLUDES)) \
 	$(addprefix -isystem ,\