Remove setting the unused variable NINJA in build shell scripts

This variable ended up unused in
b89cdef107.

build-compiler-rt.sh

@@ -68,7 +68,6 @@ fi
 
 if command -v ninja >/dev/null; then
     CMAKE_GENERATOR="Ninja"
-    NINJA=1
     BUILDCMD=ninja
 else
     : ${CORES:=$(nproc 2>/dev/null)}

build-libcxx.sh

@@ -62,7 +62,6 @@ cd runtimes
 
 if command -v ninja >/dev/null; then
     CMAKE_GENERATOR="Ninja"
-    NINJA=1
     BUILDCMD=ninja
 else
     : ${CORES:=$(nproc 2>/dev/null)}

build-lldb-mi.sh

@@ -53,7 +53,6 @@ fi
 
 if command -v ninja >/dev/null; then
     CMAKE_GENERATOR="Ninja"
-    NINJA=1
     BUILDCMD=ninja
 else
     : ${CORES:=$(nproc 2>/dev/null)}

build-llvm.sh

@@ -138,7 +138,6 @@ fi
 
 if command -v ninja >/dev/null; then
     CMAKE_GENERATOR="Ninja"
-    NINJA=1
     BUILDCMD=ninja
 else
     : ${CORES:=$(nproc 2>/dev/null)}

build-openmp.sh

@@ -52,7 +52,6 @@ cd llvm-project/openmp
 
 if command -v ninja >/dev/null; then
     CMAKE_GENERATOR="Ninja"
-    NINJA=1
     BUILDCMD=ninja
 else
     : ${CORES:=$(nproc 2>/dev/null)}