build: use full paths on compile/link targets

This makes the compile commands clearer when building in parallel (with
`make -j`) and ensures that `__FILE__` includes the full build-time path
(relative to the root of the repository) whenever it is referenced, such
as in failed assert() messages (currently the full path is only shown in
errExit() messages).  Example:

Before:

    firejail: main.c:100: main: Assertion `1 == 2' failed.
    Error src/firecfg/main.c:100: main: malloc: Cannot allocate memory

After:

    firejail: ../../src/firejail/main.c:100: main: Assertion `1 == 2' failed.
    Error ../../src/firecfg/main.c:100: main: malloc: Cannot allocate memory

Commands used to search and replace:

    $ git grep -Ilz '^MOD_DIR =' -- '*Makefile' | xargs -0 -I '{}' \
      sh -c "printf '%s\n' \"\$(sed -E \
        -e 's|^MOD_DIR = src/(.*)|MOD = \\1\\nMOD_DIR = \$(ROOT)/src/\$(MOD)|' \
        -e 's:^(PROG|SO) = [^.]+(\.so)?$:\\1 = \$(MOD_DIR)/\$(MOD)\2:' \
        '{}')\" >'{}'"
    $ git grep -Ilz '^HDRS :=' -- '*.mk' | xargs -0 -I '{}' \
      sh -c "printf '%s\n' \"\$(sed -E \
        -e 's|wildcard (\*\..)|wildcard \$(MOD_DIR)/\\1|' '{}')\" >'{}'"

Note: config.mk.in, src/fnettrace/Makefile and src/include/common.h were
edited manually.

This is a follow-up to #5871.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/include/common.h b/src/include/common.h
index 03a71967b..5f09fe3e2 100644
--- a/src/include/common.h
+++ b/src/include/common.h
@@ -41,8 +41,8 @@
 
 #define errExit(msg) do { \
         char msgout[500]; \
-        snprintf(msgout, 500, "Error %s/%s:%d: %s: %s", \
-                 MOD_DIR, __FILE__, __LINE__, __func__, msg); \
+        snprintf(msgout, 500, "Error %s:%d: %s: %s", \
+                 __FILE__, __LINE__, __func__, msg); \
         perror(msgout); \
         exit(1); \
 } while (0)