Cross-compile armv7l binaries for 32-bit Raspberry Pi's (#167)

Build arm binaries for 32-bit architecture.
Use patch based on https://github.com/curl/curl/pull/9054.

firefox/patches/curl-impersonate.patch

@@ -1354,7 +1354,7 @@ index cb162755d..13ee571aa 100644
 +
 +      case $host_cpu in
 +        arm)
-+          addlib="$addlib -larmv8_c_lib"
++          addlib="$addlib -larmv8_c_lib -l:libgcm-aes-arm32-neon_c_lib.a"
 +          ;;
 +        aarch64)
 +          addlib="$addlib -larmv8_c_lib -lgcm-aes-aarch64_c_lib"
@@ -1498,3 +1498,18 @@ index 706f0aac3..0ad94622e 100644
  endif
  
  # if unit tests are enabled, build a static library to link them with
+diff --git a/lib/easy_lock.h b/lib/easy_lock.h
+index 819f50ce8..1f54289ce 100644
+--- a/lib/easy_lock.h
++++ b/lib/easy_lock.h
+@@ -36,6 +36,9 @@
+ 
+ #elif defined (HAVE_ATOMIC)
+ #include <stdatomic.h>
++#if defined(HAVE_SCHED_YIELD)
++#include <sched.h>
++#endif
+ 
+ #define curl_simple_lock atomic_bool
+ #define CURL_SIMPLE_LOCK_INIT false
+