README.md: Fix CMake build instructions

The previous instructions were simply wrong because `cmake ..` would
attempt to configure the project from the parent directory, instead of
the build directory.

README.md

@@ -59,13 +59,13 @@ to `slcl`. If required, encryption should be done before uploading e.g.: using
 #### Mandatory packages
 
 ```sh
-sudo apt install build-essential libcjson-dev libssl-dev
+sudo apt install build-essential libcjson-dev libssl-dev m4 jq
 ```
 
 #### Optional packages
 
 ```sh
-sudo apt install cmake xxd jq
+sudo apt install cmake
 ```
 
 ## How to use
@@ -90,9 +90,8 @@ $ make
 #### CMake
 
 ```sh
-$ mkdir build/
-$ cmake ..
-$ cmake --build .
+$ cmake -B build
+$ cmake --build build/
 ```
 
 ### Setting up

page.c

@@ -1305,7 +1305,15 @@ static int serve_file(struct http_response *const r,
     dynstr_init(&b);
     dynstr_init(&d);
 
-    if (dynstr_append(&b, "%s", res))
+    if (preview)
+    {
+        if (dynstr_append(&d, "inline"))
+        {
+            fprintf(stderr, "%s: dynstr_append inline failed\n", __func__);
+            goto end;
+        }
+    }
+    else if (dynstr_append(&b, "%s", res))
     {
         fprintf(stderr, "%s: dynstr_append res failed\n", __func__);
         goto end;
@@ -1315,14 +1323,6 @@ static int serve_file(struct http_response *const r,
         fprintf(stderr, "%s: basename(3) failed\n", __func__);
         goto end;
     }
-    else if (preview)
-    {
-        if (dynstr_append(&d, "inline"))
-        {
-            fprintf(stderr, "%s: dynstr_append inline failed\n", __func__);
-            goto end;
-        }
-    }
     else if (dynstr_append(&d, "attachment; filename=\"%s\"", bn))
     {
         fprintf(stderr, "%s: dynstr_append attachment failed\n", __func__);