title: macOS llvm can't find stdio.h anymore
body: <p>I come to you with a weird problem I've been facing.
  So last week, I installed llvm and libomp for a C project, and it compiled just fine with this at the start of my makefile:</p>
  <pre><code>CC=clang
  CFLAGS = -O2 -fopenmp
  CFLAGS += -I/usr/local/opt/libomp/include
  LDFLAGS = -fopenmp
  LDFLAGS += -L /usr/local/opt/libomp/lib
  </code></pre>
  <p>Today I meant to finish that project, I opened vs code (I don't know if that's relevant), added some code left and right, and when I wanted to compile the code again to test if everything was fine, it gave me</p>
  <pre><code>me@macbookPro% make
  clang -c  -O2 -fopenmp -I/usr/local/opt/libomp/include bubble.c -o bubble.o
  bubble.c:1:10: fatal error: 'stdio.h' file not found
  #include &lt;stdio.h&gt;
           ^~~~~~~~~
  1 error generated.
  make: *** [bubble.o] Error 1
  </code></pre>
  <p>which has left me dumbfounded since it worked just fine a few days ago.
  I tried to do an export CPATH with</p>
  <pre><code>export CPATH=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include
  </code></pre>
  <p>but I got a bunch of warning and it didn't work either.
  Any help is greatly appreciated !</p>
  <p>Info: I'm running the latest version of BigSur and VSCode.</p>