Make FILE_WRITE append in SD.h wrapper (#6106)

* Make FILE_WRITE append in SD.h wrapper

Fixes #6105

* Update host tests

Author: earlephilhower

Diff for: libraries/SD/src/SD.h

@@ -27,7 +27,7 @@
 #undef FILE_READ
 #define FILE_READ sdfat::O_READ
 #undef FILE_WRITE
-#define FILE_WRITE (sdfat::O_READ | sdfat::O_WRITE | sdfat::O_CREAT)
+#define FILE_WRITE (sdfat::O_READ | sdfat::O_WRITE | sdfat::O_CREAT | sdfat::O_APPEND)
 
 class SDClass {
 public:

Diff for: tests/host/fs/test_fs.cpp

@@ -350,10 +350,10 @@ TEST_CASE("Multisplendored File::writes", "[fs]")
     f.write((const uint8_t*)&bigone, 4);
     f.close();
     REQUIRE(readFileSD("/file.txt") == "aAbbcctheendxyz@@@@");
-    File g = SD.open("/file.txt", FILE_WRITE);
+    File g = SD.open("/file2.txt", FILE_WRITE);
     g.write(0);
     g.close();
-    g = SD.open("/file.txt", FILE_READ);
+    g = SD.open("/file2.txt", FILE_READ);
     uint8_t u = 0x66;
     g.read(&u, 1);
     g.close();