tcc.h: Extend search path for include, lib and crt

This allow the tcc cross compilers to work as expected,
when tcc was build with '--enable-cross' and a simple config-extra.mak
(see the provided config-extra.mak.example).
Make sure, that cross development packages for libc are installed

Fixes also open bugs in various bug tracker. Example in debian: 940469
  tcc: error: library 'c' not found
  tcc: error: file 'crtn.o' not found
  tcc: error: undefined symbol 'printf'

config-extra.mak.example

@@ -0,0 +1,27 @@
+#
+# during 'make', this file is included from the tcc Makefile
+#
+# this is an example, how to help tcc to find
+# the c library and the startup files for cross compiling.
+#
+# we expect here, that the GNU libc is used and that the related development files
+# are installed in a subdirectory with the target triplet used by gcc 
+#
+
+# set CONFIG_TRIPLET for cross compiler targets
+DEF-i386+= -UCONFIG_TRIPLET -DCONFIG_TRIPLET="\"i386-linux-gnu\" "
+DEF-x86_64+=-UCONFIG_TRIPLET -DCONFIG_TRIPLET="\"x86_64-linux-gnu\" "
+
+# many api/fp combinations are possible for arm
+DEF-arm+=-UCONFIG_TRIPLET -DCONFIG_TRIPLET="\"arm-linux-gnueabihf\" "
+DEF-arm64+= -UCONFIG_TRIPLET -DCONFIG_TRIPLET="\"aarch64-linux-gnu\" "
+
+DEF-riscv64+= -UCONFIG_TRIPLET -DCONFIG_TRIPLET="\"riscv64-linux-gnu\" "
+# For win32/win64 targets, we expect mingw 64
+# is is for additional packes, as tcc has ist own win32 startfiles
+DEF-i386-win32+= -UCONFIG_TRIPLET -DCONFIG_TRIPLET="\"i686-w64-mingw32\" "
+DEF-x86_64-win32+= -UCONFIG_TRIPLET -DCONFIG_TRIPLET="\"x86_64-w64-mingw32\" "
+
+# is a free cross compile toolchain for macos available?
+#DEF-x86_64-osx+= -UCONFIG_TRIPLET -DCONFIG_TRIPLET="\"x86_64-apple-darwin\" "
+#DEF-arm64-osx+= -UCONFIG_TRIPLET -DCONFIG_TRIPLET="\"aarch64-apple-darwin\" "

tcc.h

@@ -260,7 +260,9 @@ extern long double strtold (const char *__nptr, char **__endptr);
 
 /* path to find crt1.o, crti.o and crtn.o */
 #ifndef CONFIG_TCC_CRTPREFIX
-# define CONFIG_TCC_CRTPREFIX USE_TRIPLET(CONFIG_SYSROOT "/usr/" CONFIG_LDDIR)
+# define CONFIG_TCC_CRTPREFIX \
+        ALSO_TRIPLET(CONFIG_SYSROOT "/usr/" CONFIG_LDDIR) \
+    ":" USE_TRIPLET(CONFIG_SYSROOT "/usr") "/lib"
 #endif
 
 #ifndef CONFIG_USR_INCLUDE
@@ -277,6 +279,8 @@ extern long double strtold (const char *__nptr, char **__endptr);
 #  define CONFIG_TCC_SYSINCLUDEPATHS \
         "{B}/include" \
     ":" ALSO_TRIPLET(CONFIG_SYSROOT "/usr/local/include") \
+    ":" USE_TRIPLET(CONFIG_SYSROOT "/usr") "/include" \
+    ":" USE_TRIPLET(CONFIG_SYSROOT "/usr/local") "/include" \
     ":" ALSO_TRIPLET(CONFIG_SYSROOT CONFIG_USR_INCLUDE)
 # endif
 #endif
@@ -289,6 +293,8 @@ extern long double strtold (const char *__nptr, char **__endptr);
 #  define CONFIG_TCC_LIBPATHS \
         "{B}" \
     ":" ALSO_TRIPLET(CONFIG_SYSROOT "/usr/" CONFIG_LDDIR) \
+    ":" USE_TRIPLET(CONFIG_SYSROOT "/usr") "/lib" \
+    ":" USE_TRIPLET(CONFIG_SYSROOT "/usr/local") "/lib" \
     ":" ALSO_TRIPLET(CONFIG_SYSROOT "/" CONFIG_LDDIR) \
     ":" ALSO_TRIPLET(CONFIG_SYSROOT "/usr/local/" CONFIG_LDDIR)
 # endif