Fix / suppress new unused warnings for mingw+clang

Bug: 69933068
Test: mmma system/core
Change-Id: I089166a979d3d8c5ada38a7745d507b555048499
diff --git a/fastboot/fs.cpp b/fastboot/fs.cpp
index 8877b09..98061df 100644
--- a/fastboot/fs.cpp
+++ b/fastboot/fs.cpp
@@ -27,7 +27,7 @@
 using android::base::unique_fd;
 
 #ifdef WIN32
-static int exec_e2fs_cmd(const char* path, char* const argv[]) {
+static int exec_e2fs_cmd(const char* /*path*/, char* const argv[]) {
     std::string cmd;
     int i = 0;
     while (argv[i] != nullptr) {