[build] Use GNUInstallDirs for NGS_PATH

Source: #669

CMakeLists.txt

@@ -15,7 +15,7 @@ include(GNUInstallDirs)
 # -D_XOPEN_SOURCE - strptime on Linux
 # -D_DEFAULT_SOURCE - MAP_ANONYMOUS on Linux
 # -D__BSD_VISIBLE - AF_UNIX on FreeBSD
-add_definitions(-D_XOPEN_SOURCE=700 -D_DARWIN_C_SOURCE=1 -D_DEFAULT_SOURCE=1 -D_BSD_SOURCE -D__BSD_VISIBLE)
+add_definitions(-D_XOPEN_SOURCE=700 -D_DARWIN_C_SOURCE=1 -D_DEFAULT_SOURCE=1 -D_BSD_SOURCE -D__BSD_VISIBLE -DINSTALL_LIBDIR=${CMAKE_INSTALL_FULL_LIBDIR})
 
 # This is workaround for boehm GC library bug or NGS usage of it
 # which cases sporadic SIGSEGV and other issues after fork() in child process.

lib/stdlib.ngs

@@ -8587,10 +8587,8 @@ section "Loading code" {
 		%[
 			${ try ENV.HOME / '.ngs' }
 			/usr/local/etc/ngs
-			/usr/local/lib/ngs
-			/usr/local/lib64/ngs
 			/etc/ngs
-			/usr/lib/ngs
+			${C_INSTALL_LIBDIR}
 		].filter()
 	}
 

vm.c

@@ -3757,6 +3757,13 @@ void vm_init(VM *vm, int argc, char **argv) {
 		set_global(vm, "PCRE_NEWLINE", MAKE_INT(d));
 	}
 
+	// INSTALL_LIBDIR - https://stackoverflow.com/questions/47346133/how-to-use-a-define-inside-a-format-string
+#define NGS_STR_TMP(X) #X
+#define NGS_STR_TMP2(X) NGS_STR_TMP(X)
+	set_global(vm, "C_INSTALL_LIBDIR", make_string(NGS_STR_TMP2(INSTALL_LIBDIR)));
+#undef NGS_STR_TMP2
+#undef NGS_STR_TMP
+
 #define FFI_TYPE(name) \
 	vm->c_ ## name = make_ffi_type(&(name)); \
 	set_global(vm, "c_" #name, vm->c_ ## name)